First biome is all about getting gems. Do this by just ignoring everything and collecting gems, or by only hunting big multi point monsters. Single hit point monsters are at best a distraction and annoyance, at worst a thorn-stealing nuisance. I actually have a hunch the optimal strategy is to bypass all seed plots and just rush the middle random room, and if you don't get something useful, to restart. Ideally, you'd get something with a positive return on investment that is an attack, and then work your way down the level, kill all the mobs and collect their gems, and work your way back up. Not difficult, but just too boring to seriously consider.
Second biome is also all about getting gems. Ideally you have some way of farming effectively from spawners, like red hot rock, or bomb, or flyseed, or star, or something. Farm the spawners. Ideally you also have either digseed or gardener by this point. Then you're laughing.
Third biome is about survival. Best tools here are digseed/gardener and star, or just reflect seed. Either of those combos will cause you to breeze through this biome with tons of extra gems and not a lot of fear of lost hearts. Reflect seed alone could carry you through this one.
By the fourth biome, you should be well stocked and as long as you have star/reflect and bomb/homing-shot, you'll breeze by.
As for the boss, what a mess. I'm not even sure. Just do what you can, you ideally have a basically limitless supply of gems by this point, and a huge arsenal of seeds. Having no way to effectively crowd control like bomb or homing shot, or something like star or cloak to avoid crowds, and you're probably done.
My preferred rollout is probably homing shot first because it is so useful at every stage of the game. Then reflect seed, or star, I'm really not sure which is better in the long game. Probably star, if I can only have one. Then, I really want digseed or gardener. I think if I get those, I don't care what else I get.