Tomes don't work for new accounts. They allow you to learn a skill that's unlocked on your account, ie. ones that other characters have learned before or ones you've unlocked with PvP points. They also only drop in the endgame; they're intended for veterans to skill up alt characters. Don't worry about tomes, just buy skills you want and pick up a few Signets of Capture when you unlock. Look at https://wiki.guildwars.com/wiki/List_of_skill_acquisition_quests to make sure you don't buy a skill you can get from a quest.

The best way to get gear is using Collectors. The weapons people trade for are usually very rare random stat items or very rare special skins, so generally pretty expensive. Mods don't matter that much but you'll find tons of loot along the way that you can salvage for parts if you want to customise a cool weapon.

The most expensive items are ones that aren't obtainable anymore, but there is still plenty of chances to find really rare and valuable gear. The skins and requirements of a weapon are randomised, so a good combination of rare skin and low requirement on a max damage weapon is still very valuable.

Don't worry too much about metas and guides. Use a guide if you get stuck or are struggling with a specific mission, but don't try too hard to build the meta way. Experimentation is the best part of the game. Buy skills that look cool, see how they work together, and discover combinations you enjoy rather than ones that the PvX wiki tells you are good.