I have now reached level 29

On my islands I have the following habitats:
2 Large Plant
3 Large Earth
4 Large Fire
3 Large water
3 Large cold
2 Large Air
3 Large metal
1 Seasonal
4 Moon
4 Sun
1 Treasure (without dragon)
(1 Kairos completed)
(1 Gemstone island with 4 inhabitants)
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Dragons except gemstone dragons:
My Plant-related dragons are on level 10-15.
My Fire-related are 40 right now on Lev 10.
My Air 22 on Lev 10 + 2 Level 15
My earth 26 + 2 level 15
My Metal 23 + 1 Lev 15
My Cold 23
My Water 17
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What strategy should I use when I buy a new habitat? A lot of you have much more experience and it would be nice to get some advice – Thank you!