Since you are on a tight budget and repainting probably isn't an option
Google: paintless dent removal methods
lots of how-tos and videos of these PDR methods
The rapid cooling and rapid warming of the metal and the PDR methods all rely on "metal memory", the body panel wants to return to it's original stamped form, the heating and cooling and small taps and leverage help it to do that.
In some places you will need to drill a hole on the inside of the body panel to get to the dent location on the outside, don't be afraid to do that, but FIRST find a rubber plug the right size for the hole you need then find the drill bit for that size plug, lol, there are a limited amount of plug sizes, not so with drill bits.
Some dents simply have to be pulled or pounded out, or the body panel replaced, and repainted