You are wise to think of waiting for the new processors to launch.
In general, a new generation brings about a 15% boost in price/performance.
This also gives you time to more carefully consider your options.
Some questions:
Are you an amd stockholder?
Or.. why the insistence on amd?
Today, Intel current gen has the edge in gaming, not that the difference is big.
No telling if the new announcements will change that.
Why RADEON which I take to mean a AMD graphics card.
New cards will be launched soonfrom AMD and Nvidia and nobody knows what they will bring.
Opinions differ on having separate devices for windows and all else.
There is no performance difference and consolidating all on a single device may be cheaper.
It is certainly easier to maintain a single C drive.
You say no monitor.
Do you already have one, or what are you planning on buying?
Do your research now, but plan on buying it all at about the same time.
There are several dangers in buying piecemeal:
a) New product announcements may change your mind.
b) You may, at assembly time find a part to be defective, but
the return window has expired.
c) Prices tend to go down, not up.
Consider the types of games you will play.
Multiplayer will want a cpu with many threads.
Fast action games will want a strong graphics card.
CPU centric games will want strong single thread performance.
If you have a pc ow, run the cpu-z bench and look at the single thread performance rating.
Here is a listing of such ratings including the currently strongest R9-5950X:
https://valid.x86.fr/bench/gskata
Cases are a personal thing.
A large case will be able to accommodate good front air intake which is essential to good cpu cooling.
Three 120mm fans, two 140mm, or one 200mm is what I would look for.
A washable front air filter will keep your parts clean.
Will you need a DVD drive?
Fewer cases of today will include such a provision.
Do you want RGB "bling"? Not for me but tastes vary.
Bust your budget if you need to for a case you really love.
Are you an overclocker?
If you are seeking to overclock a high powered processor, start thinking about how to accommodate a large 360 size liquid cooler.
OTOH, gamers of today rely on the normal turbo mechanism to boost a few cores past what an OC will do.
Overclocking is good if you have an app that can keep all available threads fully occupied.