Need advice for a newbie female at the gym

I've lost my weight so far almost purely by running on the elliptical. I started doing 15min runs at level 3 resistance, but did my longest runs for 50min at level 6.

I have just yesterday switched my routine to build muscle, however - now I do 30min runs at level 8, as well as several weight exercises. I do Russian twists (seated, 6lb medicine ball, 6 sets of 20), chest presses (just the bar because I am weak, 3 sets of 10), trunk lifts (on the bench, 4 sets of 10) and if I want to do some bicep curls, I just pick up the lightest weights I can find and use them idly until it's time for me to head to work.

EDIT: on the elliptical, I started at a pace of about 128 steps per minute, and I'm now at 144-150.

When I started going to the gym I watched loads of youtube videos to understand the exercises and how to do them properly. I never really liked machines (plus I believe that free weights are much more effective) so I threw myself into the dumbbells section right from the beginning, learning a lot of new stuff every day from the more experienced guys.
There are also many workout plans created by pros, have a look at bodybuilding.com, you just need to find one that matches your goals..:)

Thanks for all the tips. I am doing dumb bells and have increased my weight to 20 lbs and about 12 reps. And I love that elliptical machine. I was just watching you tube last night for gym workout videos.

20lb dumbell and 12 reps of what? you can do a lot with a set of dumbbells.
curls? presses? lat and front raises? chest flys? Tricep extensions? rows?

You'll lose fat by maintaining a deficit in your eating.
For gaining strength, you need to do a tried and true strength training program like strong lifts or starting strength.

If you are brand new to the gym…you might be better off starting with the basics. Skip the machines and get into the free weight area.
Nia Shanks - Lift Like a Girl is an excellent resource. As well as the book New Rules of Lifting For Women.