Answered I'm A Reboot Noob, Help Me!

Just gonna add on to Fill's reply, which is already comprehensive.

Like he said, Mysterious Path 3 is your best bet. It currently offers higher rates than Longest Ride on ByeBye Station with a 150 Kanna (about 400m/hr vs 300m/hr with 120% meso). Another alternative is Ghost Ship 2 also at around 300m/hr. The advantage of ByeBye is it's an instanced mini dungeon, so you can find a spot easily during 2x if other maps are taken. You can also farm MP3/GS2 at a higher level than ByeBye; just remember to kill your character so it stays within level range.

Leprechaun familiar is fine for meso farming. I personally preferred Big Spider for the additional drop rate to obtain nebulites, but since you just need mesos right now you should stick with Leprechaun. There's also the Eye of Time which can stay out longer, but is much rarer to obtain.

Fill's advice for accessories is spot on. Keep in mind there's a 100% mesos obtained cap from potentials. Do one at a time after each session in case you get to legendary and find the 20% mesos obtained line (or even 2-3 lines if you're super lucky). Regarding cubes, I suggest using Master Craftsman Cubes (7.5m in pot shops like Henesys) to unique, then Red Cubes (12m in Cash Shop) until you find the meso line. There are debates, datamining, and random statistics regarding which cubes are the most cost efficient, but in the end it's just rng/superstition so I'm sticking with my suggestion to just cube with what you can afford.

Your 8% meso Inner Ability is tricky; I wish it was 10% but it's not a huge deal. You can get a +12% meso gain by finding the legendary line, but it's probably more efficient to leave it and work on accessories. Save up honor while meso farming, prioritize your accessories, and once those are finished you can perfect the IA. Getting the 20% meso IA is typically cheaper than cubing accessories because you should roll to unique using honor, then tier up to legendary with Miracle Circulators (19m in cash shop). You could yolo to legendary with honor, but I suggest using the Miracle Circulators because they don't drop tiers and you usually get to legendary within 10 attempts. Usually. After that keep using the circulators to find the 20% meso line (Miracle Circs guarantee the highest 1st line).

As Fill said, Yu Garden dailies are the best source of 50% Epic Potential scrolls in Reboot. You can also obtain them from elite boss bonus rewards and the legion coin shop, but those are much less efficient (eboss is rng and legion coins are better spent on other things like meso buffs). If there is an event going on with a coin shop, there's usually a 10-pack of epots that might be worth considering if you're in dire need of them and there are no other Best-in-Slot priorities. But really just stay on top of your Yu Garden dailies. To save time, skip the tedious ones so you can meso farm more.

My final advice is to just hang in there. You have to start somewhere. Meso farming is very tedious and unrewarding at first. Cubing can be frustrating and rates will be slow. But once you start getting those meso lines, you'll see how quickly you can make mesos to progress your main. Ultimately you can get meso gear on your main and farm the hell out of Arcane River.