I'm developing my own gamemode for samp but some people tell me that Mysql is better and I should use it.

I don't know if they are right or I should continue using Y_INI.

What do you recommend? :(

It depends on your object. MySQL is a robust and extremely effective rescue system, capable of supporting thousands of requests and making personalized and simple queries that 'ini' data rescue systems cannot do without having to go through all the data beforehand. Y_Ini, on the other hand, like any 'ini' data saving system, is practical and simple to use, as they use the saving of local files.
MySQL will require more robust hosting and support for MySQL (in vps you can install it yourself), but most likely it will bring more stability to your data and you can make several implementations, such as CPU for your players and so on.
I would recommend using MySQL, due to its possibilities, effectiveness and theoretically better to support a high flow of players. However, you will have to spend a little more on hosting. So, if you don't want to increase your spending a little more, you can stay with Y_ini who will play your role in an excellent way too.
I created a topic on that too, where there is a discussion where you can look too: https://www.burgershot.gg/showthread.php?tid=1517