I have a confession: I am not a natural-born money genius and I didn’t start off working as a personal finance journalist. I used to work part-time gigs – retail, service industry, even a telemarketing call center.

When I worked those jobs, I managed to spend almost everything I made. Then one day I realized I had to shape up, learn more about personal finance, and stop buying bobbleheads of cult classic film characters (OK, sometimes I still do that).

I’d like to think I’ve learned a lot, but I learned a lot of it the hard way – through financial mishap. My biggest mistakes were actually money moves I thought were brilliant at the time.

Here are five things I used to think saved money, and why they were actually costing me money.

1. Driving to cheaper gas

It started off innocently enough. My tank would run low and I’d start looking for gas signs. I’d see one for, say, $2.39 per gallon and then another for $2.38 right across the street. Wait a minute! I bet I could keep driving and find even better deals. So I’d drive another mile, then another, then I’d see a sign for $2.37 but convince myself I could find a lower price. Twenty minutes later and I’d wasted a gallon of gas trying to save 4 cents a gallon. That makes no sense.

You should comparison shop for gas but not while driving around. Instead, use a website or app like GasBuddy.com to find a cheap (and nearby) station before you head out.

2. Biting off more than you can chew

I have a love/hate relationship with my Sam’s Club membership. The prices are great but there are only two of us and one puppy in my house. I learned the hard way that buying food from Sam’s Club isn’t always a good idea. For example, I bought a 10-pound bag of oranges for $6.98, or roughly 70 cents a pound. It was a great deal, but we couldn’t eat them all and about 4 pounds went bad. In the end I wasted about $3 trying to get a great deal on bulk food.

Bulk food is a great idea if you have a large family or you can freeze and eat the food later. If not, I’d skip buying bulk fresh produce, dairy and other foods that don’t keep. If you waste the food, you waste the money.

3. Over-investing in a new hobby

I have a bad habit of going full speed ahead with an idea before I actually commit to it. Take photography, for example. In college I saw a photojournalism exhibit and decided I was going to be the next Robert Capa. I ran out and bought a $399 Nikon camera and about $200 worth of lenses and other accessories. Six months later I realized photojournalism probably wasn’t in my future, and the pricey camera found its way to a shelf in my closet.