Panic-dodging the Fire Breath. The Fire Breath has a clear one-second wind-up where the dragon rears back. New players often dodge as soon as they see the tell, then get hit because they dodged too early. Wait for the flame to start, then dodge. Practise the timing and it becomes second nature.
Standing behind the Iron Dragon. While the Fire Breath only hits the front cone, the Tail Slam hits anyone behind the dragon. Stay at the dragon's side to avoid both attacks. Side position also gives you the shortest path to dodge either attack.
Saving all skills for the boss. Skills help you clear waves faster, which means you take less damage before the boss and arrive with more health. Use area skills on wave packs and single-target skills on the mini-boss. Your cooldowns will reset by the time you reach the Iron Dragon.
Farming Dragon Tombs for ore past level 15. The ore-per-minute ratio drops off quickly once you outlevel the dungeon. If you have the Fiery Iron Sword and are above level 15, switch to Ancient Battlefields for better material density.
Ignoring the forge between runs. Each Dragon Tombs run drops 20-40 ore. If you chain five runs without visiting the forge, you are sitting on 100+ ore doing nothing. Visit the forge every 3-4 runs to reinvest your materials.
Thinking Dragon Tombs teaches you everything. Dragon Tombs is a gentle introduction, but Ancient Battlefields and Inferno add mechanics that this dungeon does not prepare you for — floor AOEs, multi-boss gauntlets, lava pools. Use Dragon Tombs to learn the fundamentals, then be ready to learn new systems in harder dungeons.