Affordable training classes?

My 6 month old yorkie was a surprise gift from my mom. She got him from a friend of hers and it's clear her friend had him for a long time since his carrier she gave us was way too small but never taught him simply commands like sit, stay, not pulling on the leash and such. I've been teaching him and he's doing well especially with the pulling but with commands he's still not completely getting it no matter how many times I try. I use a clicker, train him only for a few minutes each day, try to make it as fun for him as possible but still far from perfect and its been about a month now. So I don't know if it's his age, his last owner, or my methods that is the problem but I'm not sure if I should just enroll him in a training class or keep trying. I'm a college student, unemployed, and on financial aid so I really can't afford anything too expensive. Anybody know of some good places I could go for some help with this without forking over 100s of dollars? Or should I just keep trying? Answers are appreciated :)