You ABSOLUTELY want to get every kingdom to 5 or 6 before taking any of them further. Not for the mastery, but for the increase in tribute chance!
Glory tribute is absolutely the best way to earn glory each week. Last week I earned about 6k glory from tributes alone. Maximizing tribute is all about (in order of importance)
1 - Get all kingdoms to level 5/6.
2 - Get all glory kingdoms to 1 gold star of Kingdom Power.
3 - Get all kingdoms to level 10.
4 - Get all kingdoms to 1 gold star.
5 - Get all glory kingdoms to 3 gold stars.
6 - Get all kingdoms to 3 gold stars.
Going for 5 gold stars gives more stat bonuses & income, but does not increase your tribute chances. This is the end-game prioritization list, which is limited by glory more than any other resource.