If you're looking for a noticeable increase in muscle mass, you need to lower the reps and raise the weight. For example, 2 or 3 sets of 10 reps with a lighter weight will tone your muscles, but won't affect their size so much. Instead, try increasing the weight to the most you can lift with good form for 2 to 3 sets of 6 reps. Logically, it makes more sense to work the sets of 6 until you are happy with the size of your muscles, then work with sets of 10 or 12 to really carve them out and give yourself the definition you're looking for. The most important thing to do, whether you're toning or bulking, is to lift to the point of muscle fatigue.
If you're looking to lose weight, then your best bet is actually to focus on your diet. It is much easier to cut 100 calories out of your diet than to work those 100 calories off after you've already eaten them. The simplest and most effective diet is a vegetarian, or mostly vegetarian, diet that is low in animal products, especially dairy products. Even if that is out of the question, just cut back on or eliminate the dairy products and limit your meats to chicken and fish. Finally, after you're all done with that, then you can finally hit the gym :D
P.S. Sorry about the essay. I wrote a lot because I'm interested in the subject and I feel that there is a lot of misinformation out there. Anyway, good luck with everything