Teenage years are weird for tithing for sure! Do you have a job?
If so then YES I would suggest a 10% tithe as it is Biblical, however all throughout the New Testament you see people giving different amounts 100% In Mark 12 the widow gives a penny and Jesus is more happy about that than the people who tithe 50% of all they have.
It is important to tithe and I recommend doing it, HOWEVER as a teen it is also important not to only tithe financially, but TITHE 100% of your life to God. When you completely surrender to Him and His will, He begins to reveal things to you that only He could. So make sure that Your life is a true reflection of Gods love, and these things will come along with it! Live a Generous Life and have faith that God will provide what you need. Take a read of James 1! I think giving is a faith issue, people who are scared to give financially have not completely trusted God with their life! If you have full faith in God you know that He will provide so tithing wont even be an issue.
Hope this helped
GodBless!