It's guppy with a y, hun. Guppies plural. :)
There are a couple of problems with your setup that you might want to rectify.
1) Guppies are social fish and really should be in groups of 3+.
2) A five gallon tank is really only meant to support one fish. They can't cope with the bioload of a betta, a guppy and a bottom feeder, especially as most bottom feeders produce a fair amount of waste. Unfortunately, this means that you can't afford to add in more guppies.
3) A 5 gallon doesn't afford a lot of space. Even if your betta doesn't have territorial issues in such a small space, it doesn't provide the guppy with a whole lot of swimming room. Personally, I don't think they should be in less than a 10 gal.
4) An unknown fish is a problem - I'm worried for your bottom feeder. Chances are it is one of two things:
a) a pleco, which get to a minimum of 6 inches, with some species getting as large as 2ft. They produce a lot of waste and shouldn't be kept in less than 20 gallons.
b) a cory, which are schooling fish, happiest in groups of 5+. As said above, your tank doesn't have the room to support such a school.
Right now, I wouldn't be adding things as your tank is pushed beyond the limit. If you want to add a snail, you really need a bigger tank.