Normally you can't gain weapon/tactics skills unless you are fighting something around the same level as your skills. For example, you may try fighting goats, cows, llamas, etc to see if your tactics will raise. There used to also be a bug that skills would get stuck around 25 and not raise at all. I don't know if that bug was ever fixed, but the solution was to put on jewelery to raise your skill, and then fight. Usually your skill would start to raise after that. But 25 is a little low. Why not buy up more skill and see what happens? I hope this helps.