Hello and welcome to Lustria!
Very awesome to start up a new Lizardmen Army. Being socially competitive is pretty much how I play as well.
2000 points starting out is a pretty decently sized army. 40 Saurus is a good starting block. If you are themed-driven, then that would help direct you in what models you could be looking at next. At 2000 points though, a Battalion box would be a decent choice to start if you didn't already have 40 Saurus (unless you plan on using another 20 of them for a large horde or 2-units of 30 etc.).
You may want to think about who you'd like to lead your army. Are you wanting a more combat-orientated commander either on-foot or rather mounted on a mean carnasaur? Then you'd want to look at the Old Blood/Scar Vet models both on-foot and one riding the awesome beast (really.. both models are great and I'd suggest at least getting one on foot). Or are you leaning towards a magic casting leader? The Slaan is arguably the best caster for it's points in-game for 8th edition currently. Skink Priests act as a great holder of dispel scrolls and assist for the Slann. If you are thinking of a more skink themed army, then I'd suggest looking at a Stegadon with a Skink Priest and EOG (Engine of the Gods). Overall, the Lizardmen shine in the Magic Phase so this is something worth considering. As for named character leaders/heroes, unless you have a very specific army theme you are wanting from the lore, at 2000 points they would really take up much of your alotment (500 points max to spend on Lords and Heroes respectfully in a 2000 point army).
To finish out your core, I'd highly suggest getting some skinks. The box set comes with both Javelins and blowpipes. The blowpipes are for skirmishers and work very effectively as screens and redirecting units. The javelin/hand weapons and shileds are more melee driven. While not optimal by themselves in much regard, imo, (meaning if you are going infantry, points are better spent on the much better saurus)) they are really great with the Kroxigor upgrade option. This allows you to purchase 1 kroxigor for every 8 skinks and put them together in a mixed unit (we call that a Skrox unit) with a normal configuration of 3 Kroxigor and 24 skinks (though some use more). For some, this can be an unwieldly unit for it's size, but if practiced and used well, are excellent flank attack units.
For your Specials, I'd suggest getting some (or converting/paint differently if funds are tight as these little guys can get a bit expensive) Chameleon Skinks. A small unit of 5 to 7 works great for me. In 2000 point games, I run a Slann, so I would invest in some Temple Guard for the mage's added protection and to allow a champion to accept challenges. If you don't plan on running a slann right away, then these could be purchased later. I like Terradons in games of 2000+. While optional, the manueverability of these guys are great and a small unit can tie up an enemy spell caster well. If you like calvary, then you could look at the Cold One Cavalry. Personally, I don't field them under 2500 point games. While their stats are decent, they are a bit overcosted imo especially in smaller point games. As mentioned above, I'd suggest in getting at least 3 Kroxigor. You could try using them by themselves in a unit of 3, or use them in a Skrox unit. Either way, they are pretty handy and offer a strong attack.
For Rares, you could use your Stegadon kit to make (there are some great threads on here showing how to make the Howdah weapons and crew magnetic to swap for the different builds) an Ancient Steg. Really, this is probably the most optimal use aside from using as a mount for your Skink Priest (Engine of the Gods) imo as the 2 giant blowpipes seem to perform better and it's a better armour save than the Special one. Salamander Hunting Parties are, imo, a must in just about any army you create. Aside from spells, they are your #1 effective unit to burn through enemy units with tough armour. Razardons can be usefull, but seem to be viewed as a shelf weight in favor of using the points for their more flameboyant Salamander cousins. That's not saying that the Razardon's are useless. They can be effective against light to no-armoured enemy units and if you can get a lot of the quills to wound, then your opponent will be hurting.
Anyways, this isn't a Lizardmen bible by any means, but more of an overall look at the most-used units in our army book and, as usual, are my opinion. I'm sure others on here could lend you some greater advice, but at least this can give you a bit of insight. Since we both share the same type of gaming atmosphere, sharing what I use more often seemed practical.
Hope this helps you even if just a little. Once again, welcome to Lustria and if you have any questions and cannot find the answers in the appropriate thread headings, then feel free to ask! We are more than happy to share our advice and help with what we can.
- Lord Cedric
(by that I mean not getting smashed every game lol) but im not about "must win" as long as both players has had fun playing.