What happens to your mouth while you are a young adult will have a long term effect as well.
Get lots of holes and fillings in your teeth now and they will have to be replaced and repaired repeatedly over your lifetime, and that costs money.
Looking after your teeth now and spending a little on prevention (which may just be seeing a hygienist once a year) will have positive long term benefits.
Brush regularly with a good fluoride toothpaste, be sensible with sweets and drink lots of beer (whilst keeping an eye on the Government's alcohol consumption advice).
Don't waste money on mouthwashes.
Wear a gum-shield if you are involved in contact sports.
When you are at home during the holidays be nice to your parents and get them to buy you enough toothbrushes and toothpaste for term time.