First of all, emphasize that you cannot sell products as such league of legends since this is a registered trademark and you cannot sell on your behalf, but you can sell products within its theme.
There are already several channels on youtube that make figurines with league of legends themes and sell them through different websites. Therefore, it is essential to have an online store to sell them.
If you like the art and crafts of league of legends, you can create a channel to promote them and then through a website, sell them to interested people.
The way to promote it would be as always through social traffic, working your brand through youtube and Instagram, especially.
Here the profits will depend a lot on the final quality of your products and the shopping experience you give the user.
This theme encompasses many facets that are complex to explain in this post, among which topics such as pre-sales, sales, after-sales, marketing, shipping, suppliers, associated expenses, etc.
It is a vast topic, and I may develop it in another article later if I see that there are people interested in it.
Alternative To ELO Boost: DUOQ
There is an alternative to ELO Boost that is not directly penalized by Riot; this is not to perform ELO boost which you can find at https://elo-boosters.com but to provide a service to the player that helps him improve without having to give him a coaching session.
It consists of whether you are a high-level player (above Diamond), offering to play DuoQ one or two games with a person who is interested in improving or learning.
And it has the advantage that it is not coaching, so you will not need to stop to analyze the person thoroughly to make him improve. The one that improves will depend exclusively on him. Your job is to teach him the tactics you use to track his games.