The best weights are free. Use your body weight. Do push ups. I found the muscles in my arms, back, stomach and chest became more defined after doing 10 military push ups a day, for 1 week, just 10. Doing 100 in 2 minutes is a good all round work out. I've never been able to do more than 35, but i know girls who can do 70. The trick is to get your form right. If you have a weak core, your form will get sloppy pretty quickly and it doesn't matter how strong your arms are.
Don't push it though. Start with getting your form right. Do as many push ups as you can with perfect form. Once your form starts dropping, that's as many as you should ever do until you've improved.
Chin ups: You'd be surprised at how much it works the abs and back. I remember one time I did 4 chin ups and the muscles in my abs were pulling my legs upwards while the muscles in my back were trying to keep my spine from dropping. It is really quite strenuous. Aim to do 10 chin ups. I can only do 4 because...well..I'm a girl and I'm quite weak.
Sit ups. You can download the sit ups cadence from various defence force recruiting websites. Bend your legs at 90 degrees, hands on your thighs, and sit up til your wrist reaches your knees and relax back down.
If you join a gym, they usually give you an induction and show you how to use the weights and stuff. I don't really do much weight lifting because I'm not trying to bulk up.
Current weight 50.4kg
Current Fat % 13.5%
Fat % 14.0%
-Si vis Pacem Para bellum-