It tells me I have to collect orchords to advance but when I set something down it takes orchids insted..

The flower count shows how much more flower you need to reach the next level, so you want that count to reach 0. So when you place a decoration on your island the count will closer to 0. When you sell a decoration, the count will show that you need more flowers. Once you reach 0, you will level up, and it will immediately show you how many flowers are needed to reach the next level.

Note that if you buy a decoration, you'll need to wait for construction to be complete and remove the red ribbon, before the flowers will count. Tip: if you buy too many low-flower decorations, you will run out of island space.