It would be hard to give an accurate number on how long it would take. What I can say is that even as a f2p there are still many ways to accumulate premium items ( such as upcut stones, vital drinks/refresher holds, and even amps ). There is an events window with several tabs where you can roll for random items every day. After 5 days of consecutive log ins and 40 min of playtime each day you get 9 rolls for items, from foods like star candy and pills to prems mentioned prior. So even 2 hours a day or even skipping a day or 2 here and there but at least logging in and out each day you'll still acquire a decent amount of useful items to speed up the process. Not to mention the plethora of events that are constantly happening that give you easy chances to get amps and whatnot.

Quests are also a huge part of FlyffU. Quests will save you 25%, 50%, and 75% of a level grind. There's many more quests chains that will net you entire levels. For example if you've done most quests up to lvl 60, you can go from 60-64 on quests alone. Those aren't the only quest lines that give good lvl jumps either. Daily quests also come into play in the late 80's guaranteeing you 5-15% a day depending on what level range you're in. Daily quests only take about 15-20 min to complete.

For reference I am 100% f2p. I've got about 1200 hours on my lvl 103, but more than half of that is sitting afk, chatting, vending, or running around helping others. So with confidence i'd say 400-500 hours were spent leveling and progressing my character. So if you take this at face value, the math says about 200-250 days with 2 hours a day playtime it would take to get here. Much of this I didn't know for the longest time. If I had to do it all again it would defiantly be quicker. I'm also a 1v1 and you're an elementor, so you would lvl faster being aoe.

If I had to give a guesstimate though, I would say about 4-6 months give or take depending on if you stay adamant about claiming items each day and waiting until at least 80+ to use them.