Most probably monsters setup or rune issue. My suggestions are (not in any order)

1. unlock magic shop so you can buy some mons or runes instead of hunting in dungeon.

2. Get wind imp or wind bear from shop or secret dungeon. I prefer wind imp though.. These two are quite often used in all kinds of situation. Wind bear 6x energy rune. Wind imp can go for blade and fatal.

3. Awaken your water fairy and rune her 6X energy. Water fairy has sleep and  heal. Can progress with her until finish faimon. Make sure rune 2,4,6 are hp%.

4. To level up faster, just do the highest level of the normal maps. Faimon node 1 gives about 700+ exp and drops a bit of energy.

5. Focus on getting % instead of numbers on runes 2,4 and 6. rune 1 gives att, rune 3 and 5 give def and hp. Remember to upgrade to level 3. Don't attempt to upgrade too high level as they will be obsolete in higher levels.

6. Having a variety of elements make it easier to beat those maps. Setup your team with mix of tanker/healer/attacker. For example, in water maps, setup 3 wind mons and 1 water/fire tanker or healer. AI enemy will always target the weaker element.

Things not to do.

1. Do not make your light garuda into food. Light garuda is quite rare considering no maps drop them and they only come from light/dark scroll. Garuda can strengthen att and revive which some people consider useful.

2. Do not make your water inugami into food. While water inu is weaker than fire, it is still useful and it can be used for fusion (to make 4 star mons).

3. Do not over farm runes because lower levels provide noobie runes. Good runes usually come from shop (6 star at lvl 30 onwards) and giant/dragon dungeon.

4. Do not attempt secret dungeon too much unless you really need to. At lower levels, the energy vs pieces gained is terrible unless u can get to lvl 7 in SD.

most easy to earn mana is by doing secret dungeons SD.
u can earn 50k 80k 100k in hour if u hunt kaw kaw.
but the weakness is in SD, ur ID dint get any exp.