from what ive seen mr limpy is the most common, so i should go with that right? which size is average for an 18-yr-old? would small be a good size? do i have to get the underwear with the little pocket thing for it and where do i get those?

I guess it really depends on your preference and how much you want to spend. I prefer the Reelmagik basic packer. You can get it in different sizes and they aren't too expensive. They're very comfortable to wear and create a nice bulge effect. You can use the underwear with the pouch but I personally prefer a harness. Reason being that the packers will shift around alot and end up sideways in your pants. A harness will keep it in place and keep it from shifting into weird positions. Peecock has some nice harnesses and are decently priced as well.

It all depends on your preference. I started with a Mr. Limpy XS and I still use it, though I've bought all-in-ones that were more expensive and supposed to be better. I'd say size would depend on what you're looking for. I knew I didn't want anything too big, but figured that the Mr. Limpy was cheap enough even with shipping that if I didn't like the XS, it wouldn't be a big hassle to upgrade.

I ordered a harness for mine. It is super slim, and I wear it under my underwear. You should get something to keep it in place. A lot of compression shorts made for sports will have a pocket for a cup, you could try that. You could try a jockstrap. You could try a tighter pair of briefs. Really anything tighter than your underwear will help. They do move around a lot if they aren't packed tightly.

I got one from SC Novelties (the 4 inch one; I'm 15 and 5'2") because it was Amazon Prime It was $14 (so really inexpensive) and they also have a 5 inch packer for $1 more. I got the SpareParts Pete boxer briefs harness/packer pouch thing and it's really comfortable and holds the packer in place pretty well. Makes for a realistic bulge too.

Although I don't wear it outside my room ever because of parents, and not being out yet.