New to exercising. Should I do cardio before weights?

Weights before cardio. Before you get tired.

I'm not 100% sure what would be best for your goals but for me, it's always do weights then cardio. I stretch, do my weight training, then do my cardio by treadmill, running outside, biking, or a combination of those. After I'm done, I stretch again. My cardio is usually pretty strenuous and I'm typically exhausted and dripping wet when done. I personally wouldn't have enough energy to start lifting after my cardio workout.

To build out definition and tone without a lot of mass, the general method is high repetitions with lower weights. For me that means 10-20 reps until I exhaust the muscle group, a recovery period, then another set. In general I do three sets or 15-20 exercises so that takes me about an hour. Coupled with the cardio of 60-90 minutes that's a pretty long workout.

Combined with a calorie deficit, you should see some movement over time. It is not unusual to see weights go up and down and you should not be discouraged if you get 'stuck'. Simply take a break, eat more, eat often, and eat healthy, but stay within your goals. I'm totally guessing that your target should be around 1450 net calories a day based on your age (assuming you want to loose 2lbs a week). Just keep it towards that and you will probably drop a few pounds every week or two. If you exercise like I described, you will drop more IF you don't eat all of your exercise. If you burn off 1,000 cals then yes, feel free to eat a few hundred cals more (you should). MFP generally recommends a very low calorie goal - make sure you use multiple sources for planning your intake limits. MFP would have me eat 1250 cals - hah! My bare minimum is something like 1650 and I've bumped it up to 2400 when I get stuck (I know that sounds counter-intuitive).

Your goal needs to be increasing your metabolism. There are dozens of techniques for this and one size does not fit all. I've had to adjust my attack many times during my weight loss program and I'm constantly adapting to my shifting metabolism. Try different approaches, see what works, abandon what doesn't. Don't worry about doing squats perfectly, as you practice, research, and learn, your skills will improve.

Good luck and keep with it! It's worth it.

Suggestions to try to help you get started that have worked for me.
1) Balance of Good Nutrition for your needs and goals use MFP to track your food.

2) Cardio: However you can get it in your day is what is best for you. If you didn’t do any videos a certain day and you go to the school gym, try doing 30 minutes of strength training first. Then try one of those boring machines (feel same way most of time, my music gets me through it). Or take some cardio classes at school if they have them.

3) Strength Train 4 Days for 30 minutes.

Workout Idea Plan: Aim for Total Time to be 60-75 minutes keeping you moving the entire time you are exercising.

Cardio: Use interval training method by doing a rest pace for 2 minutes, then all out for 1 minute; repeat; total of 30 minutes.

Week 1: Regular Week >Strength Training at 3 sets of a comfortable working weight doing 8-12 reps for each exercise. Start with the large muscle groups and end with shoulders, biceps, triceps. Afterwards do Cardio for 30 minutes.

M Upper Body - Cardio - Stretch after all your exercise is done every time!
T Lower Body - Cardio
W - Cardio
R Upper Body- Cardio
F Lower Body- Cardio
SA Cardio
SU Rest day

Week 2:
Low/Heavy Week >Strength Training to be 2 sets of a lower weight with higher repetitions. This helps to tone and define the muscles. Do Lower & Upper on same day but don’t do same exercise back to back days, or keep Upper and Lower body on separate days.

Week 3
Regular Week > Strength Train: Use same method as Week 1 or do the weights in circuits.

Week 4:
Heavy/Slow Week > Train with a heavier weight and do less reps of each exercise.

Week 5
Return to Week 1 Regular Strength Train. Always Increase amount of reps before you increase the weight.

Cardio: As your recovery and stamina improves, increase your distance, your speed, then increase your level; or try increasing both distance & speed at same time before you increase the level.
Example>Eliptical Week 1 for 20 minutes, Week 21-22 minutes, Week 3 increase your speed,
4th week increase your level.

Keep it up, you are worth it!