Good morning/afternoon/evening Subtle,
It is great to know that you are so interested in Karma and practising dharma and even think of giving a portion of your wealth away. That is generous of you. I can see so much compassion and kindness within you that I hope that you can keeping up in your way of life.
I haven't came across such stuff as best karma, I hope you understand that Karma is not a cosmic system of rewards and punishment, but the results of one's actions, thoughts, attitude triggering the results of the others. Think of it as a ocean ripples, when it hits another object, it ripples back. You can start practising the positive karma everyday and make people feel good, and in return you will be rewarded with happiness and help along the way.
One example I like to use is manager A is always bad tempered, he enjoys scolding people. One day manager A scold employee B because employee B likes to be lazy and not working, as a result employee B is hits back manager A and landed manager A in the hospital. What society view is employee B deserves to be fired because manager A is his direct manager and have every right to scold him. However, in a karma view, if manager A is not always bad tempered and does not scold anyone, he will not emit any negative karma out in the first place. And through his constant practise of not emitting any negative karma, he would not have landed in hospital. Eventually he is going to be hit by someone and landed in hospital due to his bad temper, it may not be employee B, but someone else on the street. As you can see here, if you constantly practice emitting positive karma, making other people day, people will reward you back with happiness, loyalty and help you when you required. Employee B may even be driven to work hard.
Therefore, I hope you can see here is that best karma is not measure monetary, a simple word like yes sir and no sir is different from yes and no. The word sir conveys a form of respect and is able to make someone day happy. The same goes to good morning, have a nice day, thank you. Simple words like this makes someone day. Spend some money and treating food on the people around you, or offering a dollar or more as tips on a taxi ride, simply talking to a taxi driver as a companion during the journey, or greeting your parents to eat first during dinner, can emit positive karma and make someone day. Other actions such as agreeing with others, praising others, and offering victory and accepting defeat also emits positive karma. And natural happiness will follows you through your actions and intention in emitting personal karma.
If you are in a delima in devoting time to own meditation practice & Dharma study or pursue a high-salary career, find the middle way that suits you the most. You can still meditate, devote the dharma study, pursue a good salary career, donate a substantial amount and continue to emit positive karma to others in your life. Take the life that suits you the most. Remember Buddha never restrict or force anyone to follow an exact path, he leaves a lot of space to individual for self interpretation on his sermon, he simply helps to guide people along to have them attain enlightenment on their own.
Lastly, I hope for the best in your way of your life.