Want the best answer without breaking the bank?
In this method you will have to use credits but you don't buy the 40% drink, because if you do the math youre really just wasting credits. So Here goes,
First play consecutively till you reach the 880 cap XP bonus (doesnt matter if you do it by simply playing random 3 once a day or playing alot of rounds).
Once youve gotten to the 880 cap, the next day before you play a single round of anything, Go to the Pro shop and buy the XP super boost (20%) for 1 hour at 90 credits.
Now that you have the super boost play a free 9 hole stroke play tourny. By doing this you will maximize your XP from a tourny round and you will also gain 20% on your 880 bonus.
Once you have completed the tourny round, continue playing the 9 hole tourny round until the super boost has expired.
Now the next day repeat the process, starting by not playing your first round until after youve purchased the super boost, and only play 9 hole tourny rounds.
Now by doing this you have collected 176 XP just from the % gains on the bonus.
If you compare spending 270 on the 20% boost over a course of 3 days and gaining 528 XP to spending 270 one day and only gaining 352 XP from the 880 bonus once, you can see how the math works in your favor.
Now if credits are no problem at all you can maximize your gain even further by simply buying the 270 one each day. It all depends on what your willing to spend.
Bare in mind you can repeat this process for however many days you'd like. But to get your moneys worth only buy the 1 hour duration and make sure it applies each day to the 880, if you buy a longer one youre only wasting credits on a lower return.
It's simple economics :D