Attaining Mastery (especially at Level 5) can be really tough and requires a fair bit of work and patience in order to achieve. In this case, I would definitely recommend that you focus on planting the strains you wish to master in your pot with the best lights and water pumps - the higher they are upgraded, the more buds you will receive. You'll also need to keep a very close eye on it, and ensure that you are watering it on time and swatting any spider mites that show up with efficiency.
There is always a certain level of chance with growing plants, so you might need to try a few times before you grow the best plant possible. Keep trying! :)
Overall, here are the most important factors in achieving Mastery:
- Max plant happiness
- Fully upgraded water
- Fully upgraded lights
- Great timing
- A little bit of luck