I haven't tried it in an actual game yet. But this works amazingly well in practice game.
Starting item: Fairy Charm (3mp5) to be built into mana manipulator, etc later.
5x Mana potion.
Cost = 180 + 200 = 380 gold.
Use the mana restoration for summoner skill.
Each mana potion provides 100mana over 20 sec = 25mp5. This is equivalent to Archangel's Staff.
Under ideal condition, you will also restore 12 mana over the 20 sec from Fairy Charm.
Start by smacking random creeps to make sure all of them lose some hp. Use your AoE. You should be able to kill at least 2 or 3 creeps out of the wave. Your level 2 AoE should be able to take out half HP from ranged creep without extra AP.
Use your Summoner spell before the items, so that it will finished recharging by the time you run out of potions.
Do this every other waves or so in order to not push too far into the lane and risk getting ganked. Or if you're feeling confident, use it on every wave.
When you have enough gold, get back to base and focus on building high AP. Once your spell can 1shot creeps, you're golden, since you'll be able to farm plenty to buy the extra mana pot. Use the extra gold to buy yourself good items.
@Catloaf: I'm not the best at explaining things, I guess.
Basically, you buy a lot of mana potions instead of normal mana regen items (like Meki Pendant). You then make up for the difference in the items that you would normally build into a higher tier item by being able to farm much better.