unless you can find second hand you wont get a 2k point army for 200$.
The skink box is of GREAT value. it has 24(!) skinks that can be equipped with either javelins or blowpipes. Some quick GS work will enable you to use them as chameleons, a unit almost everyone uses. Get at least one box of them, more if you want to use skinks as cohorts. (35-70$)
You will pretty much need sauruses. 16 per box is decent, but you will need at least 2 boxes for one unit. 20-25 is normal for a unit, but up to 40 is not super uncommon. 3 boxes gives you two medium sized units. Make a few unit fillers, like a statue or something made out of polystyrene to save some money. (105$)
If you want a slann, you should probably get a unit if TG too. two boxes will be needed for one unit (probably a third box or some proxies if you want to play any other school than life, since 20 is pretty few models, and without the defensive buffs and raising of lore of life the unit can quickly be crippled by shooting and the like). (124$)
The stegadon kit is fairly cheap, and most armies contain at least one stegadon. you will also get at least one skink character "for free" with the kit, so that saves a bit of money too. (58$)
Most armies include several salamanders. they are expensive, but i bought kroot-hounds from the 40k range instead. they are MUCH cheaper, and you can use spare skinks as crew (see link in my signature for pics). (25$)
The total then comes to 348-383$. well over budget, but you should be able to make a decent 2k point army of it.
If you want bargains, you can try and get hold of the old saurus models on e-bay or the like (they were included in the starter kit back in ages past and should be fairly common), or just buy second hand. If you buy painted models also buy a bottle of simple green/dettol and soak the models in it to get rid of the paint. note that this does not include any cost for paints, glues or other hobby supplies.
warhammer isnt cheap :¨(