Entering so called endgame. Any tip?

[ColorOfSakura]

Your best bet is to get your Artifact Gear (also known as AF or AF1) from your Job Quests at Level 45 and Level 50. That will carry you into post-storyline content after you complete Castrum Meridianum and the Praetorium. At that point I'd suggest running Main Scenario Roulette and Low Level Roulette daily to get bonus Tomestones of Philosophy (You can get 400 a day this way, 300 from Main Scenario and 100 from Low Level). You will also be able to unlock Amdapor Keep and Wanderer's Palace once you hit Level 50, and they give out 100 Tomes of Philosophy and 30 Tomes of Mythology. (Access to Amdapor Keep requires that you complete the optional dungeon "Aurum Vale" first.) Unlocking the Crystal Tower/Labyrinth of the Ancients can help you as well since it can earn you 200 Tomes of Philosophy and 50 Tomes of Mythology.

Tomes of Philosophy and Mythology can be traded to Auriana at Rowena's stand in Revenant's Toll, Mor Dhona for high level gear. Philosophy Tomes will let you purchase the Darklight Gear (Item Level 70) and Mythology Tomes will let you purchase the Myth/Artifact 2 (AF2) gear (Item Level 90).

You'll likely need at least one or two of the Darklight gear, some of the gear drops found in Crystal Tower (Item Level 80), or some of the crafted Item Level 60-70 gear in order to get your iLvl high enough to access Hard Mode Primals, Hard Mode Dungeons, and the Thornmarch (part of the 2.1 story questline.)

You'll also want to unlock the "A Relic Reborn" questline as soon as you are able and work towards completing it (its a semi long process, just be forewarned.) Your relic weapon is Item Level 80 and will be extremely useful for endgame content.