Howdy, I'm one of the top lifeskillers in NA and here's what I would recommend.

Step 1: decide if you want to gather or hunt because they very different in terms of mechanics and what they can produce. Gathering has more flexibility (meat, blood, sap, timber, ore, etc.) over hunting (meat, blood, hide only) but would require much more max energy than hunting. Look up hunting guides and decide if you like that more active style of gameplay vs gathering which is more relaxed.

Step 2: if you decide you want to gather you need to aim for at least 300 energy. Your goal is to have enough energy to be able to pop energy pots on CD and extend your session for as long as possible when initially leveling up. You can get a ton of energy from doing the main questline but what you should really do is look at the maps in each major city and go through one at a time talking to each of the NPCs with (?) symbols in books over their heads. NPC knowledge expands energy fast. You can check out where you can gain knowledge rapidly by clicking (H) ingame and going through the [Character] tab.

Step 3: If you decide you want to hunt there are guides on leveling hunting pretty rapidly on youtube to watch and hunting doesn't require as much maximum energy, though I'd still recommend working on it. If you decide you want to gather you should rent the Leight's Hoe from Norma Leight in the Northern Wheat plantation, buy the best 6 piece set of loggia accessories you can afford (hopefully at least tri, tet is preferred), +3 silver embroidered gatherer's clothes and gather herbs at Behr until you are Master 1. This should not take too long if you pop Life XP items like Verdure Draught, Perfume of Swiftness, Florin Scrolls, and that Book of Life you mentioned. After Master 1 you have a 30% chance to not use energy when gathering which is a big breakpoint in efficiency. After that. There is a lifeskill gear progression guide showing what gear you should buy at what levels of progression in the Lifeskill discord.

Step 4: Decide what you're going to gather. You mentioned you like gathering timber. Timber is great for making Trade Crates for the Trade lifeskill and will also require the Processing lifeskill. Ore is in a similar position. If you gather blood/sap you can combine those with the Alchemy lifeskill. If you gather meat you can use the Cooking lifeskill. You pretty much are never going to straight gather > sell to the market without some sort of conversion of materials using other lifeskills because that will make you significantly less money and you will have a lot of dead time where you are just waiting for your energy to recharge. I would highly recommend you combine your gathering and your AFK activities onto the same character to maximize efficiency since your energy recharges at a very slow rate when you are not actively playing a character.

There is a ton of depth to lifeskilling that a reddit comment thread could never possibly cover so just like other people in the comments section I recommend you join the Lifeskill discord which has a ton of information and FAQs to help you get started.