That the power level method is so prevalent and leveling the normal way is described as spell spam / boring / not a good use of time is imo one of the more major issues currently with the job (setting aside the whole limited vs normal arguments). Early spells really deserve some extra love for value/ fun, strongly imo. I leveled blue to 60 alone prior to basic instinct, did not power level, it was kind of 1 or 2 button spam for a while... basic instinct will help you a lot, but there is a power wall before some of the more exciting skills and beyond a bit of leveling revolves around healer mimicry and pom cure / gobskin (once you get those your sustain goes through the roof, and of course basic instinct but reading that tool tip should be obvious lol).
Anyway to point of thread. 1k needles (use mighty guard at same time, the spell does the same damage regardless), and basic instinct for later, then when you can get ram and dragon voice and 1k starts to fall off you can use those skills to mass murder for further levels (abuse the ice debuff as well, before combining with dragon you can get a few free attacks in the first few times at least)- which you can easily get from either relic trial, cutters cry, or the circus (circus you can't use basic instinct though). Aetheric mimicry is powerful but you will need help or to unsync it (assuming you don't have other good skills, and will be using basic instinct), once you have that and one of the heal spells (pom cure or gobskin) you can get the vast majority of other spells sub 70 without really any trouble at all. A very easy non-instance strong burst combo is tingle, whistle, then spear. Chocometeor is definitely a good one too. Bad breath on a huge group is fun. Make sure you use lucid dream to keep your mp up until you can stop relying on white wind.
Once you get a few primal spells and such you'll get to press a lot more buttons though, big damage high sustain.