Hey there. I have a decent amount of experience with H, glad I dragged myself out of my addiction though, with help. I'm wondering how you have such access to opiates, and how you got into them in the first place, but that isn't relevant.
FYI, I am referring to powder in this response. Never had experience with tar, but I'm sure it can't be too different.
Prices vary across the states, so $20 worth in your area may not be the same as $20 in mine. For me, a baggie/cap contained .1g of dope. So, it would help if you have a digital scale handy. If not, a small line of powder, a couple of millimetres wide and maybe 2 inches long is enough as a first-time user with a decent opiate tolerance to make you feel something, and you can always dose more incase it isn't enough. Please don't take the entire amount at once. Maybe split it into 4 seperate doses? I'd have to find out what kind of product you're getting anyways.
If it is indeed the powder, snorting it is the best ROA, but that is only my opinion, and the only ROA I've used with dope. With black tar, it's best to smoke or plug. Let's hope you get the former so my tips will assist you even more.
Do:
1. Have someone with you, if possible. Someone sober, preferably.
2. Keep yourself hydrated. Water is key. Avoid carbonated drinks, especially alcohol. This includes beer.
3. Have a trash can nearby or be close to a bathroom incase you do have to get sick.
4. Lay down if nausea sets in, but be careful if you are very high because you can nod off and choke on your vomit, and you don't want that.
5. If you have access to any anti-nausea pills or liquid (Promethazine and Ondensatron work wonders for me), keep them on hand. It may help to take one half an hour to an hour before dosing to alleviate the possible nausea. I'm not sure if you have ever gotten sick with your opiate use. Be careful with the Promethazine, keep it at a low dose as it and other drugs in its class may potentiate the dope and lead to an OD.
6. Eat something light, as an empty stomach will increase your risk of nausea, but if you do get sick, a lot of food the second time around isn't fun.
Don't:
1. Take the entire amount at once.
2. Fight the nausea, just let yourself get sick. This is your body's way of saving you if you have taken too much. And you will tons better afterwards, even if you lose half of your high.
3. Be in a place that is humid, this can make you feel worse and more dehydrated if you end up getting sick.
4. Take more once you've peaked. Save it for another time, you don't want to run the risk of ODing.
5. Be afraid to call 911 if you have horrible effects. They are there to help you, not get you in trouble.
6. Make this a habit. You are too young to let yourself have a heroin addiction, trust me, I was a bit older than you when I tried it for my first time and that's all it took.
PM me if you want when you get ready to take it. I'm here to help and listen. Please stay safe. I can't tell you what to do and what not to do, even though I strongly advise against it because for most people it isn't just a "one time thing." But, I'm not here to lecture you, just trying to respond to your questions as efficiently as I can.
There, I chimed in Speed King