On splints:
1. Make sure you are slowly increasing running volume / week
2. Strength conditioning (here is a running youtube with tons of great guides
https://www.youtube.com/user/TREther...ence/playlists )
3. Vit C / D can't hurt. I always forget to take it. Also: having a good diet in general should benefit your recovery.
4. Try not to run if you are still sore from the last one. Listen to your body, rest it when it needs etc.
5. Don't fu
ck with insoles. Get some good running shoes. I recommend going to a running shoe store and having them do a free workup, but you can also find out if your pronation etc if you do some more research online.