I'm assuming you'll be doing an extract batch. If so, you can do a partial boil meaning boil only a couple gallons, put the extract in and once it's in the primary fermenter you add the remaining water to top off the volume at the 5 gallon level.
If your pot can only hold 2 gallons max, I'd suggest using more than one pot. You don't want to have a boil over on the stove with wort, I've spilled some on my stove and it was a PITA to clean up.
But, like Orfy asked, more details will help others help you.
As noted, you can do an extract or extract+steeped grains batch and top off to 5 gallons in the fermenter. Don't add all of the extract up front. Save about half for the last 10 to 15 minutes of the boil to prevent overcarmelization.
Or follow the instructions in Chris Holst's online class Homebrewing for the Absolute Beginner. This is an excellent tutorial whether you use Chris's recipes or not. The big plus with this particular tutorial is that it is scaled for 2-gallon batches, so your pot is perfectly fine.
If you are doing extract batches on the stove top, get yourself 2 pots that are both about 14-16 quarts. Put one half of everything into each pot, so that you can boil at full volume. This will give you the best hop utilization and the least amount of carmelization. I recommend this over one 7.5 gallon pot, as five gallons of water on a single burner, on the standard stove top, takes FOR EVER to come to a boil... that is assuming that it WILL ever come to a boil. Some stove top burners just don't have the ability to boil that much water.
If you are trying to do this cheap, go to the hardware store, or walmart or some place like that, and get a canning pot... enameled steel, very cheap, will work just fine for now.