I've personally seen Chris Rett, a youtuber along the lines of our @Skari
, place well at an 1850, the most common point total for competitive play, ITC-style 1 day event with 11. Double CTC with a Dark Artisan. He did luck out though in that the double riptide wing and baronial court lists played each other and he only had to play the riptide wing and not the baronial court on his path to the final table vs an illegal white scars list that used Khan's benefits without actually fielding khan. Had the Baronial court list played either of them instead of the Riptide Wing it likely would have won the event, as that gent happened to also know white scars rules cold.
Note also: I'm going to ignore your listed numbers as that isn't the range this game is played at. Things don't start to hum until 1250 and 2500 is the upper end of normal with 1850 being the most common competitive total in the game.
Digressing back to the actual conversation. In the grand scheme of things a tinkers collection, that is what one who actually wants to explore the game from the perspective of a single faction or alliance should own ought to be able to field no less than 3000pts in optimum squad size without upgrades. dedicated transports are not upgrades and should be considered mandatory.
Which subsection of the faction or over-arching eldar battlebrothers alliance you should own quantity of in hitting that pt count is entirely at your own discretion and is contingent on how you want to play.
As rules of thumb: I would not own more venoms or raiders than 1 for every five bodies of kabalites owned with an upper max of 60 bodies and 12 of each vehicle. I do not play venomspam so I don't own anywhere near this max.
I do not run ravagers and thus do not own any, but would not own more than 6.
I would set an upper max of scourges at 3 if you magnetize, 4-6 if you don't and I'd build 2 units with haywire cannons and a unit of heatlances first with a second heat lance unit and maybe a pair of blaster units or a third of each haywire and heat lance to follow. I would save all the splinter carbines and use them as the basis of a sslyth build so you aren't boxed into a single monoposed finecast sculpt.
For reavers buy as many as you can afford. Competitive lists have been built that use 48. (8 squads of 6)
For flyers as a disclosure I only own a single voidraven and no razorwings, but I've seen, and made the case myself for, double black heart formations being an add on to something else to such as a harlequin masque or craftworld fire dragon pale court, something that can reliably take down armour. So I would say upper max would be 4 voidravens and 8 razorwings.
Read. Figure out how you want to play. Get those things and then expand further into a different flavor. When you run out of flavors or have a particular rule interaction you want to abuse checkout all 3 of our cousins and see if there is a way they can push it over the top and just keep exploring.
The only note everyone needs to hear that this forum will absolutely echo: DO NOT SPEND A RED CENT ON FINECAST Grotesques. It's appalling enough that GW thinks they can charge $20usd for a single Lahmian/Clawed Fiend/Sslyth/Medusae but at least all of those can be fielded in single body squads. Grotesques are 3 body minimum and come in single body blisters for $23.50 for monopose finecast. Instead buy 2 talos and 2 boxes of AoS/Fantasy Crypt horror/Flayer/Vargheists or some other equivalent scale miniature that comes in at least a box of 3 and kitbash them yourself using the spare bits, specifically the extra masks, from the talos kits.
Final note: baby steps and welcome aboard.