Right, give it a bigger pot with fresh planting medium, prune back to 2-3 buds, fertilize once or twice in the next month, and water well through September. There's not much left of this year's growing season, so they're limits to what you can accomplish. You should be able to get a much better root system and the beginning of a strong central leader. Then next year, it'll explode.
And find a place to store it that is not too warm. That leggy growth can result from a winter spent in a warm dark place.