1. Obviously, a better you on the outside starts with a better you from the inside. Good choices in food are critical. Try to avoid foods, sauces, dressings, etc. that are high in saturated fat, high calories, empty calories, sugar or any derivative, fried, etc. High fiber foods, fruits, vegetables, water, poultry, fish, lean meats. Eating red meat isn’t a sin, just eat it in moderation.
2. Drink as much water as you can, as this is a natural diuretic and flushes the body of toxins and keeps the plumbing working great. If you absolutely hate the taste (yes some think that water has taste) of water, then mix with a flavored low calorie powder mix (careful of the sugars, real or man made)
Oily skin is not a body defect and there is no need to worry about it. Teenagers are mostly affected by it due to hormonal increase. This can cause pimples and other skin related problems but it is just another phase in life. People with dry skin are prone to get acne as well.
There is no reason for you to worry since the oils secreted in the skin glands are for your good. It helps flush out the toxins and prevent your skin from aging.