As others have written, I collect what catches my eye - and I've found that Tsun's coins totally catch my eye. I don't have all of her coins, but maybe some day ....
I love lemon cheesecake and key lime pie, so when I saw YemonYime's citrus coins, I tried to collect those too.
And my most recent designer I like is Jackalgirl.
The problem is that it's often rather difficult to find out who has designed a particular coin, so I've sometimes been surprised when I finally was able to track down the designer.
Turns out my cool Alien Compass Rose was by YemonYime too!
I have other subjects I try to collect - like Japan-related coins, and since I'm in Denmark, it's also Danish made and Denmark-related coins. And Jackalgirl was partly responsible for the Four Elements Compass coins - plus some Japanese-related ones.
There might be a few more subjects ;-)