Pretty new to synths -- I own one E423 for my daughter

I am into getting a RADIAS, but before jumping into that (spending money and home-area) I thought to follow the following procedure:
1) get a midi keyboard to explore a bit of synths (in computer)
2) later use the midi keyboard for radias
3) buy new (900-1000Euros) or used radias (600Euro?)
So, what do you think about the general strategy of going into synths?
Regarding keyboard, I am leaning towards Novation Impulse 61, which says is splittable to 4 regions and has aftertouch, and some DAW. (Ableton live).
So, some more questions:
a) is a a good keyboard with splittable regions + DAW (Ableton) good to become familiarized with synths? I would like to play electronic patches (one on top of other) + basses, etc

b) Is the keyboard good for radias?
Will I be able to do anything the radias asks (area split, pitch bend)? The buttons on the keyboard will be useless, with RADIAS, right? Aftertouch will be usable with RADIAS? Can one map more midi keys to radias or it doesn't make sense( It has arpeggiator keys).
I cannot spend huge amounts of money in general.