I have this friend who is into eSports recently, which is a Dota 2 game. Back in the days, where he is only betting with his items on Dota 2 which it has value in US Dollar($).
He is really owning before, he even used his profits on gambling to pay his tuition fees on college.
I asked him how he did it and how he become owning and most of the time is winning with profits.
He answered me, "You need to focus, bet only on those game that you know".
Then I really agree to him since he is also one of the best Dota 2 players in our circle of friends, so no doubt if he knows how to analyze every team and fights in Dota 2.
In short, it much better to bet on what you know, especially in games, eSports or non-eSports.
Knowing the game, players, and deep match up analysis is the key for a successful bet. Sometimes, I was wondering if its some sort of a "talent", that youre not only good in gaming, but youre also good in looking at the match up heroes ( specifically Dota2 ). I was one of those who placed a bet using mythical items with good market values before, but Im not as successful as your friend.