To begin with you should have a moderately good cube. Moyu RS3M 2020 and Moyu R3SM 2021 Maglev are good options, for quality and price.
Now let's talk about the method. there are many methods you can learn, like CFOP, Roux, Petrus, ZZ... But definitely if you want to be under 20 you can't use the Beginners method. On youtube there are thousands of tutorials of many methods. Learn the one you like the most!
I understand that not many have a lot of time to cube, but it doesn't matter if you have a lot of time or a little, you should take advantage of your practice sessions. Not only should you practice, you should also learn things. For example: if you know reduced Fridrich you can learn a PLL or OLL that you don't know.
I assure you that if you follow all these tips, in time you will be able to be under 20.
Now let's talk about the method. there are many methods you can learn, like CFOP, Roux, Petrus, ZZ... But definitely if you want to be under 20 you can't use the Beginners method. On youtube there are thousands of tutorials of many methods. Learn the one you like the most!
I understand that not many have a lot of time to cube, but it doesn't matter if you have a lot of time or a little, you should take advantage of your practice sessions. Not only should you practice, you should also learn things. For example: if you know reduced Fridrich you can learn a PLL or OLL that you don't know.
I assure you that if you follow all these tips, in time you will be able to be under 20.