Gym newbie, please help me make a routine!

I just started attending the local gym (gold's) and am excited about getting my fitness level up.

Originally I wanted to use a personal trainer for at least a few months to help me figure things out but I'm hoping I can make a fitness plan myself and save some money.

I don't need any weight loss but would like to add significant muscle/tone up the areas that are getting flabby (using high weight/low reps). I'm doing a couch to 5k program for cardio for now. I need advice on weight lifting, I'm thinking it would be easier for me to just do upper and lower body on separate days, doing each two days a week. Right now the free weights are less intimidating to me so I'm hoping to focus on exercises with those, but I can get over my fear and get in some weight machines too :-). Am I the only one that finds the gym intimidating?!

Any advice on 3-4 exercises I should make sure to include for both my upper and lower body days? I'd obviously like to work the whole body but definitely have a focus on legs and adding muscle to my butt that has an unfortunate genetic disposition to become a pancake :-).

Thank you for any and all advice!