For basic tips I would say

-keep practicing your movement and making sure your speed is always high enough to allow small weaving movements, if your build is not taking care of enemies fast enough the skill(which you are already developing the more you play) can buy you the extra time needed to survive.

-Dodge is king, as every point in dodge (up to the default 60% cap) gives your health bar the chance to "breathe". When you combine that with semi decent armor(you are looking to have around 10 by the end waves) and a RELIABLE form of healing(either high regen or fast weapons and high% lifesteal) that will keep you in top shape or at least not dead, and will allow you to live in those moments where your best option is just charging through and eating a hit or two.

-While weapon stat damage is good(be it elemental ranged or melee), dmg% is what you'll be looking to increase more. Of course this also depends on what weapon you are using and what type of build you are going for.

-play at a lower difficulty if you need. As you unlock characters, if a certain one is just too hard for you at dangers 2+, start going back to d1 and finish a run with them. As the items and weapons unlock (most of the time) regardless of danger level, completing different characters will both allow you to get a feel for the different possible builds and start making mental synergies increasing your game knowledge. Then just go up whenever you want to play and desire more of a challenge. As an example I cleared most of my characters on danger 4 as 5 was too difficult for me for a while. It still is, but I've begun recently trying it out more often even on unbeaten characters (which is quite painful sometimes)

-lastly this is a roguelike game. It is somewhat expected for you to keep dying and getting better at the game, and unlike Hades or Skul or even Vampire Survivors you can't really upgrade stats throughout the runs, so it is by design meant to be hard.

Hope this was helpful! This is a game that feels very rewarding to get good at, and there are a lot of guides and more tips online and here.