Coming back to the game after over a year away. I don't know what new stuff is worth getting or how much to get. I was hoping to get suggestions on starting.
Lambs and Lions has a good suggestion to play some games to get a sense of things. But if you're looking to get a quick sense of the new landscape for Seraphon after the new battletome, I'll try to give you a quick rundown.
It's important to note that the new battletome's official release was just a few weeks ago, and the new models came out then as well. We are are still learning the new army, so take anything I say with a grain of salt.
The troops are also a bit different depending on whether you are playing Starborne or Coalesced. Both factions have strong magic, but the Starborne magic is stronger and more offensive, with teleportation and very good summoning. Coalesced is tough and has new monstrous rampages for each Seraphon monster. Neither faction is extremely fast or extremely strong with shooting or melee, but the magic helps mitigate this with strong and flexible buffs and debuffs. Many of the units feel over-priced, points-wise, but the magic mitigates this. With magic and abilities, both armies are very mobile, and can do a lot of board control. Starborne leans toward many cheap screens and Coalesced has some decent anvils, but both factions can do either approach to a point.
Also, we lost some units, including the Skink Priest (we have no priests now), Eternity Warden, Saurus Sunblood, Saurus Knights (but they were replaced) and Razordons. The Salamander was changed to the Spawn of Chotec and the chameleon skinks have become the Hunters of Huanchi, with different weapon options.
Here's a quick rundown, starting with the units that are new:
Raptadon Chargers - the new skink melee cavalry are very good, and are the most point efficient attackers in the army, especially on objectives. The are fragile glass cannons, but are cheap and fast. In Starborne, they can be summoned pretty easily, potentially 7" from an enemy, and get +1 to charge rolls, allowing them to steal objectives or deal significant damage. They are battleline in the Fangs of Sotek subfaction, where they also benefit from the free redeploy ability. They are cheap enough to use as wide oval-based screens. The base is the size of the Saurus Knights' base.
Raptadon Hunters - the ranged skink cavalry are okay, but not amazing. They buff the Raptadon Chargers, and are buffed by them, but it's usually going to be better to just bring more chargers instead. The base is the size of the Saurus Knights' base.
Aggradon Lancers - the new Saurus Cavalry are the fast hammers of the Seraphon. Unfortunately, they aren't that fast for cavalry, or as tough as a lot of other armies' cavalry, but with proper buffs, they can go very fast and be quite tough. People are just starting to get the hang of them, but I've been hearing good things. They are battleline if the general is a Saurus, which you can do in Coalesced but wouldn't usually want to in Starborne. In Coalesced they are also tougher and get +1 to would on charge in Koatl's Claw. They are less point efficient in Starborne, but still can serve a useful role there. The base is larger than the Saurus Knights' base.
Saurus Scar-Veteran on Aggradon - this hero can buff the Aggradons once per game. He's is underwhelming on his own, but could be good in a heavy Aggradon list, or if you need a cheap general so you can allocate points elsewhere. This base is bigger than the other Aggradons' bases.
Spawn of Chotec - the new Salamander is good for the cost. He no longer dishes out mortal wounds, but can still shred screens and chaff with his 12" ranged attack and decent melee profile. In Starborne, he's another good unit to teleport in to have him shoot and maybe charge. He also has an alternate 24" range attack that is unreliable, but if it does damage, the enemy unit gets -1 to save. This can be a useful threat on the board and occasionally debuffs an enemy. The base is larger than the old salamanders' bases.
Hunters of Huanchi - the new chameleon skinks are similar to what they were, except now they can't be seen at all when they are more than 12" away or while they are in cover, so they can't be targeted for shooting or enemy spells. They can still go back into reserve to teleport over two turns. You can get them with dartpipes with venom that do mortal wounds, or with clubs and bolas. The later is cheap, and so great for nabbing objectives away from the battle.
Lord Kroak - still very strong in both factions. His signature spell, Celestial Deliverance, was upgraded in several subtle ways. It can now be cast 4 times instead of 3, the casting value stays at 7, and the range went from 10" to 12". Kroak's base is much bigger than his old model's base.
Slann Starmaster - still very good. It lost Comet's Call on the Warscroll, which is now part of the Slann spell lore for Starborne only, but it got some new Warscroll spells that are decent. This base is also much bigger now.
Saurus Oldblood on Carnosaur - better than ever. It has rend now, and doesn't bracket so fast. As a general, command traits and artefacts can make it extremely deadly for its cost, or you can use those to enhance the army's mobility and objective control. It can issue two of the same command for one command point every single phase, which is amazing!
Saurus Oldblood - he seems okay, but there's nothing phenomenal. Fairly cheap though.
Saurus Astrolith Bearer - he hasn't changed much, but it's as essential as ever for the magic boosts.
Saurus Scar-Veteran on Carnosaur. Everything about this is the same as the Oldblood on Carnosaur, except that instead of being able to issue two commands per phase, he has a damage ability that will, on average, do a third as much damage to an enemy hero or monster as it has previously taken at the end of the combat phase. So it's likely to kill any enemy that has only 25% of it's wounds left. Not bad.
Skink Oracle on Troglodon - this hero is excellent now! It can still vassal cast for the Slann at any distance, but now it's much tougher and possible to buff defensively to the extreme. And it regenerates D3 wounds in both players' hero phases. It has a 9" -1 to hit aura around it, making it harder for your enemies to hit it or your units around it. Enemies can't use Inspiring Presence within 3" of it, and the Warscroll spell can make it very difficult for your enemies to move around and charge. It's powerful in both Starborne and Coalesced, but will likely be used differently in each.
Skink Starseer - this model has become amazing, with two spells per turn, a great Warscroll spell and a great ability. It's very cheap for what it is.
Skink Starpriest - still very good, because skink spells are good, but the Serpent Staff ability is not as amazing as it used to be. The ability hasn't changed, but our units just won't dish out the mortal wounds with it that they used to.
Skinks - they are very good as cheap, mobile screens that can run and redeploy very well (they roll 2 dice and choose the best one). But they can't be buffed like they used to, so no more big hordes to deal crazy damage.
Saurus Warriors - super good, especially on Coalesced. They are finally tanky, able to absorb a ton of damage. They have 2 wounds, get a 3+ save in their own territory or on objectives, and in Coalesced they absorb damage and get +1 to wound on charge in Koatl's Claw. They are also still decent in Starborne. They finally have rend. They get bonus bite attacks that deal mortal wounds, which are stronger in Coalesced. Great reinforced in units of 20.
Saurus Guard - like Saurus Warriors, but they always have 3+ save, are a bit better in melee, but come in units of 5 instead of 10, so don't dish out as much damage because they can't be in as large a unit. They can now absorb wounds for all non-monster heroes, not just Slann, which is great for protecting skink wizards and the Astrolith Bearer. They get bonus bite attacks that deal mortal wounds, which are stronger in Coalesced.
Kroxigor and Kroxigor Warspawned - two types of Krox with slightly different pros and cons. They are good in reinforced units where they can attack from the back rank for significant damage. They get bonuses around skinks. They get bonus bite attacks that deal mortal wounds, which are stronger in Coalesced. They are good, but probably a little over-priced.
Bastiladon - The Solar Engine isn't as good as it was, but it's still good. With -3 rend, it can do damage to hard targets. It's probably overpriced, but it's still an important unit in the army. The Ark of Sotek is better than it was. It's pretty cost efficient, but serves a less critical role than the Solar Engine. We're not sure if this is an error, but the skink keyword was removed.
Ripperdactyls - they're okay. They are cheap, fast flying units that can target ranged units and maybe do some damage without getting killed on the way in.
Terradons - cheap and very fast. The fastest screens in the army.
Stegadons - good, but not like they used to be. They can't be buffed up like crazy anymore. They count as 10 models for contesting objectives, which is good. They are overpriced. In Thunder Lizards, they are battleline and don't count as behemoths, so you can bring a lot of them.
Engine of the Gods - nothing like it was and not great. It's not a priest anymore. It's basically a Stegadon that trades some abilities for a chance to heal every turn or cast an attack spell every other turn. It's other abilities aren't worth trying. Definitely overpriced.