What Is the first muscle group thats going to make you look the biggest??

You need to work them all, otherwise you look weird.

Here’s a good full body weightlifting routine. 3 sets of 8-14 reps of these: (each set, increase weight by 5 or 10 lbs and do less reps than the last set)

MONDAY AND FRIDAY - LEG DAY

Squats

Leg press OR dumbbell lunges

Leg extension

Leg curl

Calf raises

Leg raises (on Roman chair)

WEDNESDAY AND SUNDAY- UPPER BODY

Bench press OR chest flies

Lat pull

Incline bench

Upright rows

Shoulder YTL

Shoulder shrugs

Biceps/triceps supersets

You cant really just work on one muscle group to look big. You've got to work them all.

Focusing on one muscle group will just make you look silly (Cue obligatory missed leg-day joke). However, one muscle group that is often ignored or forgotten about that makes a big difference is apparent size is your lats. They make your chest look broader, and are important for actual physical activity, not just lifting weights. Work them out with dips, pull ups, pulling/moving imbalanced objects, and I'm sure there's many other ways.