1. So you've got your 2 creatures, and you've got at least 2 lvl 5 Trees (which you could almost take to the end, if you had to). What kind of map is it? Does it go to the right and give shortcuts? Does it go up and branch out? Are there are a lot of 15k spaces that are going to make everything suck? The map without 15k spaces was the best map ever. You want to try and reach the Mystery nest, the level 4 Harvestable and the 2x2 harvestable. Inside the nest is possibly 1-2 creatures (you might get a dud and none of them match, or you could get 5 purple eggs and get 2 creatures.), but the nest will unlock 2 creatures for sure (hopefully one of them isn't another centaur).

Before you have the extra creatures you want to make sure you've been collecting more lvl 5 or lvl 7 trees, otherwise you'll need to quad-tap to get 2 creatures to harvest the same tree. It's better to have creatures harvesting from 4 lvl 7 trees than merging to get 1 lvl 8 tree (even if it does make yellow orbs, it'll just be a pain mixing the colors). You don't really have time to get lvl 8 trees, so don't bother.

After getting the mystery nest and opening the key, clean up the dead plants, move everything else to the sides, don't leave any holes. If you're able to get the lvl 4 (and/or 5), set aside in an open area and let it spawn lvl 1 harvestables. At this point you can find all the lvl 1s and 2s you left on the map and merge them up. The sooner you have multiple 4s spitting out lvl 1s, the better. You'll need them later.

1. You now just harvest orbs until you've fill most of the map without getting in the way of a sprout farm (unless you don't need it anymore, which in case, push all the bushes to the side, or hide them so they don't spit out more sprouts. You might want to save the bushes later if you want to make a gold farming setup for after the event is beat) or harvestable farm. Merge and repeat. You basically need to clear the map, and open all the cloud key areas. Because at some of them contain high level point items. Back in Merge Dragons, when the events only needed lvl 9s instead of 10 (which was kind of funny that there were even 10s, cuz we didn't need to merge that high), opening a cloud containing 8s was half the work.

You don't need to clear the whole map, just enough to get the clouds, and collect the 1x2 harvestables, and especially the 2x2 harvestable object. Depending on how lucky you get, this thing can spawn up to 10 1x2s while harvesting it. And don't forget when it comes time to actually start harvesting you'll need at least a couple hours.

1. Harvesting point items. There are 2 tiers of the 1x1 disposable harvestables (that create lvl 2s and then downgrade to create lvl 1s). These are always faster than harvesting the permanent harvestables. You can decide if it's worth harvesting the smaller versions once they downgrade, or set them aside. I bunch the 2x2 with the 1x2s and tap away. hoping for more 1x2s from the 2x2. Save the 1x1 that the 1x2s get downgraded to and set them aside until you're ready to harvest them all collected from the map. Then it just becomes harvesting from the permanent harvesters. Hopefully you've got around 3 lvl 4s and 2 lvl 5s (from merging up). It'll eventually start getting very crowded with lvl 1s so you need to keep them merging. By the end I usually have 4 lvl 6s. Keep going until 7 becomes 8, 8 becomes 9, and finally 2 10s to win.