My favourite thing to bet on in football is the goals market as I often find it to be the most profitable, and I much prefer having to support goals than a particular team. In recent months I have found +1.5 goals to be the best option, as it is fairly likely to happen in any game (around 80% of games in most European leagues). The odds are adjusted accordingly so you only really get odds around 1.2-1.3, not a great return on its own but if you can find 5 or more on a weekend, then (if successful) it can be very rewarding, either doing them as singles or including them in multiples.
Personally I prefer to find games with trends for goals in the first half as well as +1.5 over 90 minutes, and trade out early on after the first goal. For not much risk this can produce a return of around 20%, not bad for less than 45 mins work.