A lot of people when first start playing r6s realize how many operators there is and have their minds mixed up on which one buy first, next etc. And I can see that they always ask friends, reddit, fandom, discord whoever but not themselves (sounds very pathetic rn but you're going to understand me soon).
What I always say to those people is - "shut up!", and here's why: all operators have their different abilities and playstyles associated with them and there's a lot of them! Some ops encourage aggressiveness, some require slow and strategic approach, but if you ask somebody "what op should I buy next?" in 80% of the time that person is probably going to name his favorite operator (which totally makes sense but isn't very objective)
So guys, listen - DON'T ASK!
Buy each operator based on seasonal order or don't buy any at all and save up some of that money for the time you already got some of that experience and watched quite a number of guides.
Alternatively you can play some operators with no strict playstyle you have to obey:
-Zofia
-Ash
-Rook
-Doc
-Jager
-Sledge