Yeah that's why I spent a bunch of time before the release doing as much research as I could and filtering out the shitty guides. There were plenty of guides telling you shit like "you should farm Thirain to trusted first to get +10 kindness" and it's like, that's 80k rapport you're wasting" on a really hard to cap zone for 10 stats, even though you get plenty of virtue stats if you do all the rest that's much easier. I figured if I need kindness, I'll just bomb the NPC rather than do Thirain. And I check every NPCs like that. I also figured I'd focus on giant hearts first and foremost, and for these I didn't need many virtue points.
For Giant Hearts right away my plan was to do as few rapports as I could, which is why I got started on Tooki asap(although I missed the spawns the first few days before I knew how it worked, so I was like 2 or 3 days late). I picked Calvassus and Beatrice as the 2 rapports needed for 12 hearts, because they were BY FAR way lower than the others. Sasha wouldn't have been a bad pick though with Ignea Tokens in mind, but Nineveh was an obvious trap between the high virtue reqs, high rapport and being on a fucking island so all you get is an island token with it.
Gravel
as I mentionned in the posts I actually didn't get too many legendary gifts from vendors, they're really not common, I only farmed merchants for like 2, or 3 days I forgot exactly, but I only got like 4 or 5 legendaries from that. I had a bunch from island quests(a few give boxes), events(login events the first month, welcome challenge, shit like that) and starting week 3 of the game I bought out every weekly rapport packs in the shop(they sell 1 legendary box + 3epic boxes for 120crystals, x5 times a week, all selective). That's where all the legendaries came from, not really the merchants. The merchants did have a lot of epic gifts though, and while these look meh, they add up really quickly. A lot of gifts are 330points, and if you get the "right" ones it's 450(selective boxes always give you these, and merchants give you some for specific NPCs, for example Yuul in Anikka or Morina in Yudia). You can usually buy 4-5gifts every 30mins or so, sometimes less sometimes more, but yeah camp that for a few hours every day and you come out with a lot of "free" rapport.
A large part of that initial push though is the one time relics you get for 80% tomes, as well as the couple from events. That's 100k rapport right there when I had all of them, which obviously is a substantial amount when I needed like 380k or so. Bit more if everything at 0 but once I started farming these I spent a week running rapport actions only in these zones, on high value targets, so that was like 4.1k rapport every day going towards that amount. But ultimately it was quite a lot of effort spread out over a decent duration, just the last push was very quick when I found out how easy it was to farm merchants. My original plans when I did the math that I mentionned here was to get it done over the next ~2-3weeks with the daily rapport actions and buying the shop boxes and stuff, but that basically got compressed down to like 3days when I started doing merchants(but still took 5days or something due to daily gift cap which I forgot about).