The key to getting stronger is to master the fundamentals.
Spend a lot of time just standing.
40 minutes once a week is great.
15 minutes a day is a must.

Moving qigong in its various forms will supplement standing, training the body to move in the correct way.
Form accomplishes the same.

Partner drills build up awareness and sensitivity.
The ability to affect another person.

A striking post or wallbag ensures that your strikes possess power, rather than just being empty.