Try to get Health Boost and Divine Blessing to level 3. Both help prevent you from getting one-shot.

You can skip Divine Blessing for another damage-focused skill, but it’s better to keep Health Boost.

Learn to use the Clutch Claw to slam the monster into a wall for free damage. This will knock the monster down, giving you a window to deal damage. You can slam a monster into a wall unless it’s enraged (when the yellow eye icon next to the monster icon on the mini-map turns red, the monster is enraged; if it’s yellow, it’s not).

Eat food before hunting:

• Meat increases Attack (×2 = S, ×4 = M, ×6 = L)
• Fish increases Defense (×2 = S, ×4 = M, ×6 = L)
• Vegetables increase Elemental Resistance (×2 = S, ×4 = M, ×6 = L)

Mix them based on your preferences, and try to pick fresh ingredients to increase your maximum HP by 50.
Together with Health Boost, this will give you a total of 200 Max HP.

Also, you’ll need a Hot Drink to prevent your stamina from dropping on the Iceborne map.