I was just after abit of advice please, i am thinking of buying some photoshop software to help me with my drawings and after looking at a few web pages i didnt realise there was so many different ones on the market and how expensive some of them are..

ranging anywhere from £75 to £800

Do any of you,s guys use photo shop,and if so, which 1 do you think would be best for me to buy to help with my drawing, grids, composition etc, or there is there any free download programs out there that would do the job just as well
Thanks alot for your help, and i hope this is the right place to post this question.
Lee