I'm biased towards Illustrator since it's what I use at work and for personal stuff, but I've heard good things about Inkscape. Never heard of CorelDRAW before, I'd have to do some research before recommending that.
Honestly if it's just circles and grids you could probably get away with using pretty much any vector tool, but if you ever want to do more complicated art then I would recommend finding a program you particularly like.
This website has a game of sorts to help practice manipulating anchor points and curves. It also has practice for combining and subtracting with simple shapes, which is also super useful in vector work, especially for really simple stuff. Both games are at least worth trying once, if just for the practice!
https://bezier.method.ac/If you want help with anything more specific feel free to shoot me a message! I might not be a super big help but I do have a decent amount of experience with vectors so I'll try my best ^^