Hi! Actually, I'm here to give a few tips about pricing. I'll divide this in sections.
Time/effort spent: This is a basic guideline you can use, it doesn't have to be followed at 100%. As any artist, you're offering a service, and your time to accomplish it has a value. Consider the minimum wage in the USA is $7.25 per hour, and use that to assign a value to your pieces depending on how much time of continuous work it takes you (so not counting breaks). If a fullbody takes you, for example, two hours, you can stablish a minimum worth of $14.50 (or $15 to make it whole). Some artists use lower or higher prices depending on the demand of their service, but we'll come to that later. If anything, I do suggest not to charge less than $5 for any piece; art is commonly underrated by society and lowball prices just reinforce this view. You work has value.
Demand: We see this a lot. Artists with more following have way higher chances of being paid more than less-known artists; it's the truth. This is because the demand of their services is higher. This is where the haggling comes. See what other artists with similar style are charging, see how many following (public exposition) you have, and how many people would be willing to pay for your stuff. It's more personal, but using the previous section you can rise or lower the price accordingly.
Your current situation: Are you a full-time artist? A student? Have a degree? Is it just for extra cash? (I know you're a minor but ya know, to consider for the future). Depending on your academic level and current economic situation, you can rise or lower prices. Lower prices are quick cash, while people who depend on it for a living and/or have a degree would go for higher ones. This is completely up to you. Just remember to readjust your prices when you actually open comms in some months, things might have changed.
Sorry for the long monologue, I hope it helped!