We also have a roof terrace that is sunny & can get quite windy; we grow lots of different things in pots from lobelia and alyssum to poppies, lupins and foxgloves. For climbers/cover; nasturtiums (great for climbing , leaf cover and colour - and both leaves and flowers are delicious), Jasmine (good climber and scent), Honeysuckle (particularly good in shady spot). We planted lots of stocks this year too which are pretty robust and have great perfume and colour and attract lots of bees. As for budget we grew most of these from seed or v small plants - no ground frost on a roof terrace and things thrive which you'd think wouldn't.