In my eyes Serif's PhotoPlus and other programs (PSP, Gimpshop perhaps, but it seems to be no longer developed) are closer to the big photoshop than Elements (which is just too crippled and dumbed down). Likely you are learning more relevant techniques using PhotoPlus. Lots of choices.
I would definitely recommend a recent version of Elements, 4 or
later, then your experience can be directly transferred to Photoshop,
thogh bear in mind that Photoshop is decidedly expensive. Personally
I would bid on cheap used Elements on Ebay.
An alternative approach would be to decide that the Photoshop
approach is going to be too expensive in the long run, and decide use
the free Gimp with the Windows GUI, it is supposed to be almost as as
powerful as Photoshop and regularly updated.