As you have your plants in pots already, and have a successful watering regime I would go for lots, lots more in pots. start with tulips, daffs and other spring bulbs. Go for a few varieties only, and choose by colours that you like... say pots of orange tulips, alongside others with purple tulips. Grow dahlias in pots, again put 3 of a single variety per pot, for maximum effect. Lots of annuals as well... go to your local GC and choose the ones you like on the day. Pot up en masse, water, feed (liquid tomato fertiliser is best, added when you water), the more the merrier.
As you don't have much storage room, and if you can afford it, go for new bulbs, plants etc. each year and bin the old ones as they die off. In a large garden the rest of us can overwinter our dahlias, daffs etc. Annuals always have to be replaced, and tulips mostly don't repeat well.
Anyway others will give you alternatives, or will critique my ideas....... patience and your forum friends will soon be adding to this.