Here are four good options for training skills with a low-level paladin:
1 - Yalahar Servant Golem with explosive arrows (requires completing mission 1 of the Yalahar quest);
2 - Gargoyle with small stones or other low-attack ammunition;
3 - Slimes with small stones, but, remember, never let more than two slimes attack you, otherwise they might kill you;
4 - Offline training: if your account is free, the maximum level you can advance is 50, but if you have a premium account, there is no limit.