How significant is crafting in Path of Exile, and is there a way to significantly improve my health or energy shield pool? In my playstyle, which is solo self-found (SSF), all of my gear comes from drops, Alchemy Orbs, essences, or using the Harvest crafting bench. This is my approach to obtaining upgrades from drops and ensuring my resistances are capped:

Firstly, make sure to enable "advanced mod descriptions" under the UI tab. With this setting enabled, holding Alt and mousing over items will allow you to see their prefixes and suffixes. Items can have up to three of each.

When I receive a drop that has life and at least one resist, I check if it has an available suffix. If it does, it means I can craft an additional resist on it, so I keep it for later. If it has an available prefix, it means I can add more life if it doesn't already have it. I check the crafting bench for relevant recipes that could benefit my build and ensure that the drop can have that desired stat added. Throughout this process, it's crucial never to neglect life and resistances, especially when using a Tabula Rasa.

When picking up a rare item, try to ensure that the base type supports the socket colors you need. This way, you won't have to use an excessive amount of Chromatic Orbs to obtain the desired colors. Armor/Strength gear tends to roll more red sockets, evasion/Dexterity gear more green, and energy shield/Intelligence gear more blue. Alternatively, you can acquire the socket recipes in the Delve, but I understand that not everyone enjoys running the mine.

Before starting Act 6 or Act 10, I equip the gear and then, using my crafting bench, attempt to raise all my resistances above 75%. Once my resistances are capped, I proceed to add sockets and then link them for the necessary skills and support gems.

Occasionally, I may need to buy a piece of gear from a vendor and use Alchemy and Chaos Orbs until I find something that improves my character. Purchasing gear from vendors for basic crafting purposes can sometimes be better than relying solely on drops because the item levels are often higher than the zones you're currently exploring. Higher item levels increase the chances of obtaining better tier stats.

If I can't manage to cap my resistances, I make sure to have a flask that provides protection against that particular element, such as dispelling freezing, burning, etc.

Essences offer a form of targeted crafting. For example, using an Essence of Greed guarantees a life roll on any item it is applied to. While other stats may not be ideal, at least you know that you will have a life stat on the item.

Even utilizing the most basic crafting methods can significantly improve your character's stats. My advice is to learn how to effectively use various orbs and crafting benches to enhance your drops if you don't have the currency to trade or simply prefer to play without trading.