How can you get a bigger butt and stronger and bigger calves and thighs without going to the gym or using weights?

The following advice on leg exercises is applicable to males and females, alike...

...You need to perform weight lifting leg exercises using heavy to moderate weight. You should be on a high quality weight training program, eating enough calories (bodyweight x ~18) and enough protein (bodyweight X ~1.0grams/lb. of bodyweight), and be getting about 8 hours of sleep per night.

For calf exercises, perform both standing and seated calf raises. Do 3-5 sets x 5 reps of standing calf raises with heavy weight; and do 2-4 sets x 8-10 reps of seated calf raises. Do this (within your overall weight lifting program) 1-2x/week. See link down the page entitled "calf exercises" for more information.

For developing your thighs and butt, you should perform heavy compound exercises such as deadlifts, squats, leg presses, lunges, RDLs or step ups to name a few. Don't bother with leg curls or leg extensions (unless you use them to warm up or cool down). Any good weight lifting routine includes effective leg exercises within it's structure (see links below for "Weight Lifting Program" & "Leg Exercises" for more complete information)

Another

There are 2 main types of muscle-building: 1. Condition training. Build muscles that are small and hard but can exercise for a long time. 2. Body building. Build big muscles made for short but heavy exercises.

Therefore, do heavy leg exercises which you won't be able to stand for long. Like running or biking as fast as you can. Or use a device to lift weights with your legs.

When Weightlifting, use the maximum weight that you can faultlessly lift for about 6 or 10 times in a row.