I don't suggest you relying with skills at the early stages of the game. True, you'll be using them most than attacks, but not until you finish Shadow Yukiko, you won't have a method of recovering SP other than the Soul Drops, and those will be very rare.
Try to go for a more balanced approach at first, leave the SP attacks for more tough enemies, or for a large group of enemies.
Oh, and at first when you can fuse, try to fuse a Valkirie with Media, it will help you immensily at the early stages of the game. Also try to fuse a Slime with Resist Physical (you'll learn it at Level 7 Slime) because it will be an invaluable tool to help you survive the first mid-boss attacks and bonus boss attacks.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
