It sounds like your tension wasn't consistent, it's really common (and sooo easy to do if you're not paying attention. I still have a dodgy tension!).
www.ravelry.com is hands down one of the friendliest communities I have ever had the pleasure of being a part of. There are thousands of patterns in their online database, many of which are free of charge, you can filter them by user-rated difficulties, and there are dedicated forums for technique help. I've heard that knitting simple scarves, etc, is the best practise for stitches. There are various Yotube videos on each stitch, though I sadly can't recommend a particular one (any where the person doesn't waffle on for five minutes before showing barely 30 seconds of the stitch....).
Anyway, do you have any pics of your pot holder? I'm sure it looks great - the best thing about hand-made items is that they aren't perfectly uniform in every way