skullcrushers should be your meat and potatoes for triceps, your triceps is what gains your arm size so i would do
skullcrushers
dips
extensions and pulldowns
if you want mass go onto a 5 rep for each set routine
or a 4 set 12,10,8,6 rep scheme they are great for gains
eat right a lot of
protein and try to get in about 15-20 sets a week in arms if that seems to much than move it down to about 12-15 good luck