i have a simple rule: - the more you put in, the more you will get out.
If you want to be a good competition dancer, you should practise, train, several times each week. Three 2-hour sessions per week would be fairly typical: the more the better. The steps are relatively easy to learn. It's your shaping, body positioning, smoothness and all the little things that go together to make a couple look 'interesting' and worth watching - those take all the time.
Anyway, dancing is such a delightful and enjoyable activity - why not do it as much as you can???