You'll see that peptides aren't going to give the same dramatic effect that you can get from steroids, at least not in as quick of a time. Its more like dripping water into a bucket, one drop at a time. It feels like its taking forever to fill but then at some point, you look at it and it's half full of water. Peptides are a much slower transformation, but may be ideal for someone like yourself who has already gotten a lot out of gear alone. I would commit as long as you can to using them. If you've been gearing up and training for over 15 years, I'm not going to talk about how important your diet is going to be in all of this, and I'm going to cut straight to what works, so you can make some decissions.

IGF LR3 is one of the faster acting peptides. You'll see some good pumps if you use it preworkout. The more you use, the faster it stops becoming effective. For this reason, I'd suggest a low dose. Maybe 25-35mcg, taken preworkout. At that dose, you can go through a 1mg vial, then take 3 wks off and repeat. You can use this, and other peps on or off gear, but "on" is going to give you the best gains. IGF isn;t going to get you very lean. 

GH at a dose of 4-6 IU can be effective with test. With this, there is a little more commitments. I'd run it for as long as you can. Years!!! if possible. The "water in the bucket" analogy strongly applies to growth. You'll find youself holding less fat and storing more nutrients as muscle, but to see real results, I'd suggest hitting hard with gear and commit to at least 5-6 months. IGF can be run in conjunction with growth. IMO, its a good combo. 

Of the secretagogues, I find GHRP6 and 2 to work to some expent. I have heard good things about hex and cjc, but have not used them myself. This catagory of peptide releases more of your own natural GH. They can do a good job of it too. I have used GHRP in the evening, before bed, then taken my GH in the AM, with some good results. GHRP seems to spike IGF levels quickly and I'm more likely to go hypo while dieting than on GH. 

The most powerful of all peptides is Insulin. It can be very dangerous. It works outstanding for some, while it makes others overly fat, QUICKLY! I never suggest insulin people who have an endo body type. Combining insulin with GH, along with gear has created some monsters...it has also ruined some otherwise beautiful physiques. 

If you just want to get your feet wet, IGF might be a good place to start. If you want to make a larger commitment, I'd suggest using GH along with a small dose of IGF pre or post workout.