You will definitely need a trainer to help you build muscle with the correct diet, eating is just not enough to build muscle. Depending on your age and body type you may supplement yourself . Quality food, planned exercise and genetics will help you, don't overdo it, have a routine.

Supplements that may help you

3 Grams of Pyruvate daily 1 gram with each meal (1 big red apple has about 500mg of Pyruvate)
3-5 grams of L-Carnitine daily 1 gram each meal, you may take one gram 20min before exercise
Taurine, chromiun picolinate, DHEA, B-Complex 100 to 150 mg daily,

You need to eat before the Gym for energy purposes, slow warm up of 20 minutes, then your weight training, then a cardio,bycicing is great for developing big thigh muscles.

If you get a trainer, make sure the trainer looks like he has followed the advice that you want. Don't get a trainer that does not look like he has done some work on his body.