IMHO and my apologies to PSP users but:

If you are at all serious about ever using a computer for graphics, bite the bullet and find some way to get the funds to get Photoshop. It is THE paint program, and that is not likely to change ever.

If you learn a different program now, you will just have to unlearn it and learn Photoshop someday if you ever want to do pro work. Maybe if you are a student you can get an educational discount on an older version somewhere and upgrade later (I am still using PS 7 myself).

(I used many paint programs over the years, on many different platforms, starting with a TRS-80, a friend of mine wrote one of the first paint progs for the IBM PC, and I was a contributing editor for Avid, the old Amiga magazine, so I know a little whereof I speak.)