From the beginning if you buy the Crystyalin Flask and the mana pots and the Faerie charm you are on the right path. Mana will be the limiting factor to start if you spam too hard. If the first time you recall and you can afford the needlessly large rod, I suggest buying it. and a few mana pots and going out OP for the next 10 min as you started with enough magic pen where you can delay getting the sorceress boots. Otherwise buy the Chalice of Harmony to fix you mana problems. As soon as that is covered buy as much AP as possible.

The great thing about having the hybrid rune set up is you start with 15 magic pen and 18 armor pen plus 8% pen on each through masteries. This means that the auto-attacks that brand does in between casting do significant damage throughout the game. Most people you encounter you will be hitting for close to 100% damage once you get sorcerer's boots.
The reason you have health per lvl runes is for when you get spell vamp going. Brand can be melted easily before your spellvamp even kicks in because most time you will be focused because your gonna be the beast of your team if you play it right.

Make sure you land your stuns with Brand. This is key.

Try not to use your spells to farm at the start. Use your mana to hurt the other champion your laning against, and your auto attacks to get the farm.