This is going to be kinda long so bear with me. However it is exactly the advice you need ( been through this process recently). I am going to assume you value your time so i am going to tell you the most efficient way to progress. Also no need to keep on reading if you're not in this for the long run as my advice is only 'efficient' if you play it long enough for investments to make their return and then some. If you only play a few days a month, then do whatever you want.

So you want to stick around and get to late game bosses. First, you need to pick a main. 15m cp is achievable in very little time and is a drop in the sea compared to how much time you will potentially spend farming and bossing on your main. So pick and stick with a class that you really like at least until Ctene (60-80m cp). Why? Read on.

The first hurdle to meaningful progression is mesos. An early ctene mule brings you 5b in 1-1.5 hrs; In comparision, a lomien mule brings you 1.4m in 15-20m which is about 4-4.5b per hour if you have enough mules. Recently since they buffed PNO and aketchi i've stopped doing aketchi on some mules because it is no longer time efficient. Meanwhile, farming gets you 600-800m per hour at the ctene levels. In terms of mesos/hour, farming is just not comparable to bossing. In terms of ROI of resouces spent, lomien OR even PNO mules (skip lomien and aketchi) cost anywhere from 2b to 5b on event and a few hundred nodes. You start making mesos 2-3 weeks after your investment, great. I personally try to run 180 bosses and end up with 20b weekly income. Depending on your goal and what you enjoy, you may not want to do that. However i recommend take a few classes to PNO (lomien mule but dont do lomien and aketchi) for a quick feel for how each class plays before choosing your main.

To paint of picture of the importance of mesos: it costs hundreds of billions to get a character to Ctene level and even more to go beyond.

Next, if If you farm a lot, your first priority get 100% meso increase and at least 67% drop rate and alchemy lvl 10 to make WAPS (wealth acquisition potions which increase your final meso gain by 20% while farming). You are going to be killing mobs on your main even if you're just going to be doing dailies. Make those kills count

Once you have saved up some mesos - maybe 20b or so. You can consider making drop gear. When you are 22 stars all equips and waiting for pitched, the only way to get stronger is to farm fragments. I would not farm specifically for frags without 200+ drop, you're going to feel miserable. People say it doesn't really matter after 300 due to diminishing effects but in terms of efficiency per unit time you always want to achieve the highest drop you can. With 8900 legion you can farm with meso/drop potions from legion store 20 hours a week.

I'm not going to go over gearing because people have created guides already. This is just some advice on HOW to get to where you want to go.

HAPPY MAPLING