Okay,

1)In the first picture, how can I get my hair to have that kind of wave??

2)And in the second picture, I like how the girl on the left doesn't really have a part, its just all coming from the same spot and has more volume, how can I get my hair to look like that minus the headband?

maybe for the first one, print the pic and go to your hairdresser and ask for a loose perm?

Garnier have this spray stuff that textures your hair sort of like that first picture.

2, the headband is hiding her part (it's on the side).
But at the back, it's all brushed back and sprayed.
Your hair naturally parts.

For the second:

brush your fringe to the side, take a horizontal section of your hair from the back (about the middle, between your hairline and your neck and backcomb it, then brush the hair above it over it so it looks bouncy and neat and spray it with hairspray a bit to keep it in place.

1. Scrunch it gently, with NOT TO MUCH gel or hairspray.
2. Tease it, dear.

In the first pic, the girl has sort of a beachy wave. I think she scrunched it.

In the second pic, you can also use a volumizing spray (or hairspray if you prefer). But to get the poof she has, you'll probably need the help of a headband. You would have to wear the headband after you brushed through your hair. Then, starting from the back of your head around the crown, brush your hair upwards a bit until you get the amount of poof you want.