How to Expand a guild?

Hello, I'm trying to start my own guild but I just found out that I can only have 15 members in the guild and after that I need to buy members certificate for 400 coins so I was wondering, is there is another way to expand my guild or do I need to pay 400 Coins for every member I want to invite into my guild?

you can also buy certificates with gems (495 gems = 2 licences)

Some guilds charge a joining fee to cover it. Not a good idea as not many will join but could do that.