I hate to sound like a salesman for Artix Entertainment since they don't pay me to endorse them, although I do suggest you purchase a Dragon Amulet (preferably the full account plus 2,000 AC's for $34.95) and an Elemental Unity for $5.  Preferably during a 25% or 50% off sale.  If you feel comfortably buying a $19.95 or even a $49.95 DC package, go ahead and do so, may come in handy upgrading bag space.  Although even if it's not a 25% or 50% off sale go ahead and get Elemental Unity and the Dragon Amulet.

If you join during June, for the love of God, purchase a Doomed Dragon Scythe of Elementals for 500 DCs!  It's upgradeable, and has all 8 major elements, and at level 90, is the second or third best weapon for all 8 major elements, and until then, is THE BEST as far as I know!  If you don't join during June, get it the next June.

Start grinding defender's medals during wars, upgrade your defender's dragon jewelry.

When not during wars, grind Dr. Voltabolt's Challenge.

IF THEY ARE WORTH IT (as they usually are), buy LQS gear.  I was on vacation when the Gloom Glaive rolled around (the only one I missed), I really regret missing that one.  Almost wish DF had an IoDA like AQ Worlds, almost, lol.  Although that would not be fair to those who did get it.

Start doing the Book 1 and Book 3 quest lines, especially Book 3, you will need it for Inn at the Edge of Time challenges and some of the best gear in game is from quests!

Obtain at least the following classes:  Paladin (free, Necromancer (free), Death Knight (free), Soulweaver (free), Chaosweaver (1,800 DC's), and Pyromancer (1,800 DC's).  Paladin and Necromancer are required to unlock Death Knight, and Soulweaver is required to unlock Chaosweaver.  Necromancer SUCKS in my opinion, however, Death Knight is one of the most powerful (if not the most powerful) free player classes (especially combined with its relics) and necromancer and paladin are both required to unlock it.  Soulweaver is not bad, especially when altered with Baltael's Aventail, not as good as paladin, but better than necromancer.  Paladin is pretty good (not quite as good as doom knight, death knight, or said dragon coin classes though), especially when enemies deal light damage and you need to have defense against light and / or you need to deal light damage against enemies weak against light.  Chaosweaver is a burst class, it is THE MOST POWERFUL at burst DPS, more powerful than even Doom Knight, although it sucks at defense, so you have to use it carefully in Inn fights, some inn fights it is extremely difficult or impossible to use it in.  It will save you a lot of time when grinding Time-warped Medals though.  Pyromancer is probably the most or second-most versatile Inn class as it has everything, one of the most importantly for Inn fights, DOTs!  There is nothing or very little Pyromancer does NOT have.  Watch Inn challenge videos, usually the first or second challenge completion was done by a player using Pyromancer!

As soon as you're strong enough, start grinding challenges at the Inn at the Edge of Time, using the other resources I have featured on this website (partially because I am lazy and haven't compiled them myself, partially because I believe credit is due where it is due), to min-max gear.  You will desire everything that is worth getting (not absolutely everything, I don't have absolutely everything, although I have the majority of it) at level 90, although the Legion Bracer you can obtain at Level 1, and it's best in slot for the entire game!