As the title says, I haven't worked out in quite some time. I am 23 and I would really like to get into shape, put on SOME muscle. I am 5'9" and weigh about 130 - 140 pounds, so I'm pretty tiny. I have asthma, so I am kinda limited on what I can do. Running is very very hard for me because of it. I tried doing P90X last year and I couldn't finish any of the videos, but surprisingly I did finish the Cardio work out. I had to take a couple 5 minute breaks but I did finish it. My friend wants to do Insanity with me, but I really don't think that is the best idea. I really don't have much muscle at all. My arms are tiny and I think doing these work out routines isn't the best way to start. Eating well for me is very hard because of my financial situation, but if you can throw me some ideas I will see what I can do.
I wouldn't recommend Insanity. Most of the exercises are high impact and intense and you need to be in a good shape. It's not for building muscle. It is more to burn all the fat you have. Some people that don't eat properly during Insanity will lose muscle mass as well, because they're not taking in enough protein to maintain the muscle they have so this workout is not a good option for you.
I did it and I didn't lose much weight. If you want to build some muscle you should eat right, increase your caloric intake, get enough protein to support muscle growth, work harder but shorter, and rest. You should also limit your cardio training. While doing cardio is great for fat burning, it can limit muscle growth by burning up glycogen and amino acids. You should do a lot of weight-training. Work your whole body by doing squats, push-ups, crunches, etc.
First of all - there's no universal workout plan for everyone. Both food and training should be adjusted to your body type in order to get the best possible results. Your body type is ectomorph. I suggest you to read some articles on this topic.
You should also take a look at this e-book: Bulking For Ectomorphs. You'll find some tips there.
Basic principles of ectomorph training program are:
Nutrition is also very important. Without proper nutrition, you won't get good results (especially as an ectomorph). Therefore you need to find some information about fitness nutrition. You could start with this great infographic
You wrote your financial situation is not the best. Well, you don't have to go to gym and still you can gain some muscles. You can use your own bodyweight, you would then perform pushups, pullups, dips etc. For more information on this topic, try to type Barstarzz to Youtube. They have many how-to videos online. You should spend your money on food in first place because you won't grow if you won't eat properly no matter how hard would you train.
I hope this helps a bit and I wish you to get stronger and bigger!