In Final Fantasy: Mystic Quest, you will come across little Grey tile areas you can enter. These are called battlefields.
In battle fields, you will fight ten sets of enemies, to get EXP, GP, or even a rare item or spell. This is where the majority of your experience comes from in the beginning of the game.
Below is a list of the battlefields, and what your rewards, and enemies are. The "MAP #" represents the number on the map below the table. This will give you the location of the battle field you are looking for.

MAP #	BATTLEFIELD #	ENEMIES	REWARDS
3	1	Mad Plant, Poison Toad	54 Exp
5	2	Basilisk, Mad Plant, Poison Toad	Charm
6	3	Basilisk, Minotaur Zombie, Sand Worm	150 GP
9	4	Mint Mint	99 Exp
11	5	Mint Mint, Giant Toad	300 GP
12	6	Mint Mint, Giant Toad, Scorpion	Magic Ring
14	7	Edgehog, Giant Toad, Scorpion	99 Exp
16	8	Desert Hag	600 GP
18	9	Desert Hag, Lamia, Mage	540 Exp
20	10	Sphinx, Phanquid	Exit spell
21	11	Freezer Crab, Gather	744 Exp
23	12	Jelly	900 GP
24	13	Jelly, Sting Rat	Gemini Crest
25	14	Plant Man	816 Exp
27	15	Sting Rat, Plant Man, Flazzard	1200 Exp
29	16	Flazzard, Red Cap	Thunder spell
31	17	Red Bone, Ghost, Zombie	1200 Exp
34	18	Iflyte, Stheno	1086 Exp
40	19	Ooze, Skuldier, Water Hag	2808 Exp
40	20	Water Hag, Vampire	2700 Exp