Anyway, to be honest, I still have 1 or 2 months of saving money
Ah good, if you have time then wait and research :- ).
the same goes for a case, is it worth spending more money on that?
Absolutely. A good case contributes to better cooling, easier installation, modularity of future upgrades, and last but to me most important, to silent operation.
All-time favourites like Fractal Define R5 even include 3 high-end fans in the package so you don't need to order additional ones (and you don't with single GPU).
About the Ram, so it is better to use more GB of cheaper ones?
Today, yes, in almost every situation. For certain applications, highest overall speed affects minimally the overall performance, but in 3dsMax, rendering, Adobe Suite,etc.. it doesn't do anything at all.
So simply going for reliable brand and best value/performance model is the go-to solution. Last year that was Crucial model, but I honestly don't know what the current popular favourite is.
As for more, if this is "budget workstation", then you can certainly live with 16gb just 'fine' (sort of..) but I wouldn't be able to work with it. I work with 64 and regularly fill it up on everyday basis, but 32gb is just right for average freelancer right now imho.
Also, is there anything new that is going to be released in following months that would be worth waiting for?
Sadly not at all. Skylake-E or whatever high-end platform will come soonest is year away, and I doubt it will be any more impressive then current Haswell-E. Same go for GPUs I think...
But no matter that, the evolution right now is slow, you never regret even if the next best thing comes 2 days after your purchase. Golden rule to live by is to buy what you need, right when you need it.