For most beginning football players, finding a balance between comfort and safety during football practice can take several attempts. Some items, such as shoulder pads and soft pads in the pants, will be required by your coaches. In other practices you will only wear your helmet because there will be no contact, but several other items should be considered.
What you wear under your shoulder pads is strictly a matter of comfort. Your school will likely give you a shirt to wear, but it might be a half-shirt that leaves the midsection exposed. While this helps to keep you cool, you may be scraped or cut more easily. If you practice in cold weather, you may want to wear long sleeves, and it hot weather you might want to wear a shirt with the sleeves removed. Remember that this shirt will likely carry a permanent smell, so it should be a shirt you do not plan on wearing in public.
Whether you play receiver or offensive line, you might like wearing gloves on game day. However, only wearing them on game days can cause a problem. For offensive linemen, practices are brutal on the hands. Defensive players are constantly hitting them, and you are constantly grabbing and pushing with them. In one week of practice hands can be bruised and cut, and fingertips and fingernails can be torn. Because of this, you may consider using last year's game gloves in practice this year. Reusing these gloves protects your hands, and allows you to still have new, good looking gloves available for games.
Ankle braces are needed more at higher levels of football, when the speed of the game and the size of the players make sharp cutting more dangerous for ankles. Most high school programs only tape the ankles of players who are recovering from an injury, and ankle braces can serve as an effective replacement. In some programs, athletes are required to have ankle braces on at every practice, but many do not require this so the choice will be yours.
The worst thing you can do is wear the wrong shoes at practice. Poor footwear can ruin a practice. At some levels you will be provided with a pair of cleats. You should wear these in a few practices to get them broken in, and then only wear them on game days so that the padding and shock absorption stays fresh. During most practices you should wear an older pair of cleats, much like you might wear last year's gloves.