'I'm quite a good card magician. I'm no Lennert Green, but more than competent.
Should I continue to learn card tricks and become the best I can be at it.
Or, should I branch into other areas of magic & become a good all rounder?
Life, home, and work don't really allow for both.'
Great news that you have found your passion in magic. It's fine to have a favourite field of study, and many magicians focus on card magic. If you are concerned about it, then you may want to think about the following:
What are your goals?
Why are you learning magic? Is it to go out and perform or simply for the love of learning? If you want to perform, your selection of material should be based around the ACT you want to present.
If time is short, use a practice drill technique
You really don't need a lot of time each day to set aside for effective magic practice. The secret is short, frequent, and focused sessions. Take a look at this advice about creating a practice drill program for your magic.
Hope this helps