Are there any machines (that aren't over 50 dollars) that help you tone your butt, and in my case make it bigger?

I got good news for you. If you have a pair of dumbbells you can make your butt bigger. First the weight should be so you can do 6-8 reps to failure. Squatting will do the trick. Also a barbell would be more suitable. This should cost less than 30 dollars.

Are 5 lb weights good? Those are the only ones I have.

If you are really weak. I suggest going to a gym for a day and find the right weights then purchase it.