I don’t think native synths in ableton or bitwig will help you learn the basics. They are good, but their interfaces don’t translate so well.
Pigments is one of the best soft synth. Modern, all-in-one, intuitive. Can’t recommend it enough.
You probably won’t buy Reason, but Europa, Complex-1 and Grain are so good, powerful and easy to use. And you’ll learn the basic language of subtractive, modular and granular synthesis with them.
And if you really want to learn how synthesis works go modular. Try Bitwig Grid, try Max, try Reaktor, try VCV Rack. It will enormously help you deal with any synth you’ll ever meet.
Lowend101 dedicated machine is the Analog Four, but i cover a lot of the basics here and it’s totally free with an eBook you can download in the thread of the same name here or on the website itself :
Probably a good spent of money would be :
I would go : UHE DIVA
And Then : SERUM, PHASE PLANT
Don’t forget Trial version to test VST Synth before to buy
If learning signal flow, routing and how audio works under the hood i would go with Voltage Modular and this tutorial :
I really like arturia pigments. It can be really simple virtual analog, wave table, sample/granular based. I think it would make a great learner synth as you can start simple and go as deep as you want. the UI is excellent and the modulation available is amazing.