you can add tags with the creator studio app on mobile...
But keep in mind that titles and descriptions are important as well (perhaps even more important than tags). So you should have specific/descriptive titles, and specific/descriptive descriptions. One thing I see in your tags is that they aren't very "searchable"...for example, you have one title called "I DID NOT CLICK DAT - Clash of Clans Gameplay"...while "clash of clans gameplay" is searchable, it's also fairly generic, so it's likely to have a lot of other videos as competition. However "I did not click dat" is not really something that people would search for.
Your description mentions "war attacks"...is this something that is more specific? If so, you should have that in your title. For example, if I begin typing in youtube "clash of clans war a", then there are autosuggestions for "clash of clans war attacks" and "clash of clans war attack strategy"...so that's a very specific key word, but since youtube shows it as an autosuggestion, that means people have been searching for it.
I think you'll find that if you can do specific videos (such as strategy or tactics), then that will probably have a higher chance of getting views than "just" gameplay. But to best target these tags, you'll want to make sure that your title, tags, and description reinforce each other.
