If you want suggestions on which beys to buy, it's probably best to use the 2/3 rule for parts in my opinion. Anything that's a 3/3 is practically a must.
For GT beys:
Ace Dragon - Buy. Sting is basically the bets disk. Charge is a fantastic driver.
Slash Valkyrie - Skip, layer is far outclassed besides the Valkyrie chip and the driver sucks. Only redeeming quality is the disk which is really good. The disk might show in a future random booster though.
Bushun Ashura - Skip. All of its parts are far outclassed.
Wizard Fafnir - Unsure. Wizard might be good. Ratchet is good as it's barely outclassed.
Cosmo Valkyrie - Unsure. Cosmo might make a comeback if it finds a use like Orb Egis right now. Driver is great.
Dread Bahamut - Not the Random Layer Collection version. Waiting for a full release to judge.
Judgement Joker - Buy. Best GT layer. Comes with the best number disk.
Zwei Longinus - Probably buy (waiting on testing). Good layer that can beat Cho-Z Spriggan, Hell Salamander, and Wizard. Decent disk. Decent driver.
To comment on your future purchases you suggested:
RB15 Dead Hades is a fantastic purchase. One of the best attack layers, 2nd best frame, and the best attack driver.
Cho-Z Achilles is also fantastic. Amazing layer, best number disk, and it comes with the best launcher.
Dead Phoenix is also fantastic if you don't have an Atomic and you have Revive Phoenix. You meet those 2 conditions. Yeah, 0 is great too, but it's falling out of favor. You should buy this.
Give us Assault' re-release, Iron', and Charge'. Give a non-limited re-release of Cho-Z Achilles.
Legend Spriggan on tall attack drivers for Burst Limited is fun.
Against layer powercreep in Burst Limited.