The horse must always faster than you. If it is so, then it is ok.

30k exp is a little too much for players lv 5x. Normal exp on 1 straw chicken for fires is between 2k and 3k exp. And sometimes over 3k exp.

If fire get between 2k and 3k exp, then water and earth will get between 6k and 9k exp.

Those exp rates are always better than training in Oslya, aren't they? Don't be disappointed if you only get between 2k and 5k exp from each mob (between lv 10 and 20). If there is a double exp event, those exp rates will be doubled.

Read more in the Goddess Training Guide. Be sure that you understand it completely. If you don't understand something, just ask me there. Then I will answer you in very details, if it is needed, then I will even add pictures for visual aids.