One of the greatest tools you will ever need to begin your fitness journey. Knowledge is power!

http://www.freedieting.com/tools/calorie_calculator.htm

figure out your ACTUAL base caloric needs. From there, either get into a 300-500 cal deficit or a 300-500 cal surplus. Do not go for crazy amounts over what your body needs or doesnt need. It will only result in gaining too much fat, or burning through your hard earned muscle.

Slow and steady wins this race for both goals. Get on a proper diet and track your intake through an app such as MyFitnessPal. Get on a proper training program too - this will ensure your maximizing your potential inside the gym.