The 2020 edition of the Make It Rain Campaign is still underway in Final Fantasy XIV and grants an extra 50% on all your MGP earnings.
The Mini Cactpot is a mini-game in which you can participate three times every day.
When playing Mini Cactpot you need to choose a total of three slots to reveal, then select a line on the 3x3 board. The sum of the numbers on the line you selected corresponds to an MGP reward.
User yuryu on Reddit created a Mini Cacpot (available here)that gives you advice on which slots and lines you should select to get more earnings and here's how it works.
FFXIV Cactpot Solver by Yuryu
1) You will first need to buy a Mini Cactpot ticket from the Mini Cactpot Broker in the Gold Saucer (X: 5.1 Y: 6.5). You will then be presented with your grid and a first number.
2) You will then need to input your number in the corresponding slot on the Cactpot Solver. The website will then advise you to reveal one or more slots by highlighting them in blue, select one then input the obtained number on the website.
3) Once you have revealed your fourth number the website will then highlight in green the line it thinks would be the best.
4) All there is to do now is to trust (or not) the solver and select your line! Here I tested to trust this system (I usually do it all by myself as I think it is more fun and like to gamble and greed in video games) and here's the result.
The solver can give good and bad tips as in the end it's all luck and the website is only helping you to chose slots that could maximize your benefits.
You can also be like me and click on three random slots, select a line you like, and hope to get the jackpot, the most important is to have fun!