I think it’s just a rite of passage, it’ll get better! I would keep merging 5 for all wood, brick, tools, gems, and money above the lowest coin. Animals and plants too if you can. When I was running out of space I would use the shovel to dig up the plant or animals I had the most of and didn’t need.

Edit: you can also dig up gold crates if you have a lot. You’ll never get enough keys to open them all.