Leveling tips or "roadmap" for beginner?

Hey! I am currently trying out different classes to find out which appeals to me the most. So far I lean towards Guardian and Warrior in terms of how they feel but thematically I like Necromancer.

While I'm looking forward to spend some time leveling character (most probably multiple characters)—I was wondering if there is any "roadmap" you guys would suggest me to follow? Or maybe some sort of tips? For example trying out professions/jobs for crafting stuff? Or maybe leave it for later?

Previously I was leveling by doing personal story quests and simply going through starter zones finishing them to 100%. After finishing 3 zones to 100% I decided that for the next zones I'll do hearts/quests only to gain EXP but will explore them to 100% later—after getting faster/flying mounts, that way making exploration little bit more "accessible". What do you think about it?

I am not looking for "FAST" leveling guide. I don't want to blast through "things". I prefer to do them slowly–that's more enjoyable way for me. Basically it's about quality rather than speed.

I've also got all the expansions or DLCs (grabbed them on sale). Maybe I should focus on them or specific content/systems/features they provide at certain point? An additional side question regarding expansions: how do I even access them?

I'd also like to add note that I am pretty new to MMOs. I've previously played ESO and little bit of WoW but I quickly learned that experiences from past MMOs can't really transition to GW2 in many ways (combat, questing, UI etc.). At least that's how I feel but I might be wrong.

PS. This whole need for a "roadmap" or tips came from single pain point I've encountered—I tried to do a solo dungeon on "Story" difficulty but died right at the first boss. I don't know the name of the dungeon but all I can tell is that it was meant for level 40 and I was level 46. Dungeon also looked like "manor" where I had to talk to few guests before the first boss appeared and destroyed me. It felt like it's my fault and I've previously done something wrong in my leveling that is not allowing me to get through the "Story" difficulty content.

Thank you very much.