Heya!

EtG is a rogue-lite (not -like) because the loot you discover in every run gets added to your overall pool. You do indeed lose that run's pickups on death, and start each run "fresh" without them... but new things will get added to the loot pool during each run, giving you better options and leading to synergies (where certain items held at the same time get better/change function)

For example, there are some early-game weapons/passives you can buy in stores that are not found in the chests yet, until you buy them once.
There are also NPCs that you can unlock that bring with them opportunities for more unlocks, or other useful mechanics.
Also, after clearing bosses, there is a form of persistent currency that also leads to more unlocks.


To add to what Pouyou-pouyou said:

2. If you have armor, upon getting hit, you activate a blank effect. So it counts as both a half-heart (1 HP) AND a blank.

3. I'll add that if you find a heart container item (generally looks heart-shaped, but isn't your standard red health pickup), these items not only give you an extra whole heart (+2 HP containers) BUT will also heal you to full health the first time you pick it up!
Also, if you're at full health and find a red health pickup, you can press a button to teleport it into a health-dispensing NPC, which can then be found in the shop & by the exit elevator. But I don't recommend this - better to leave it on the ground and come back for it later, because you'll be able to see on your map exactly how many HP you can heal (the health dispenser doesn't tell you this), and you don't need to find the shop or clear the boss to get to it. The health dispenser only works for the level you're on, too.

4. I've got some suggestions in the next section that are generally useful, but will help with bosses too. Otherwise, bosses are a matter of learning their attack patterns and phases.
My recommendation is to try and play through each boss on your own at least once (the challenge to figure it out yourself is fun!). Then go look up a YouTube video, preferably someone's hitless recording. Study the boss' attack patterns *and* how the player moves through the attacks.


And here are some general tips I tell most Gungeon newcomers:

- The Hunter is probably the best character to start learning with - her crossbow does great damage at range for a starter weapon, very useful for the boss fight and bigger enemies.
Her doggo also has a small chance to find loot on clearing each room (and this is separate to the general room-clear loot rate)

- focus on your character, NOT what you're shooting at. By doing this, you're better able to focus on walking around bullets and avoid dodge rolling.
Dodge rolling locks you into a direction (as opposed to the freedom of movement you have by not rolling), and you don't have i-frames for the whole roll anyway. Way more likely to get hit when you roll everywhere. Try to save your dodge roll for really hairy moments, or big attacks that have to be dodge rolled through. And, obviously, platforming parts.

- optional, but REALLY helpful: play with a gamepad with aim assist setting turned up.
I, and several of my friends, didn't believe this was necessary until realising that gamepad + aim assist = frees you up to focus on your character/walking around bullets, and not get as caught up in aiming like you would with a mouse. A lot of the really good players you can see on YouTube with no-hit runs use this method, too. :)

- avoid unlocking every *locked* chest you find, and wait until you've cleared the level (excluding the boss). Unlocked chests are fine to open immediately.
The reason I suggest this is so that if you have - for example - only 1 key, but 2 locked chests, you now have the freedom to pick which one to open. But if you'd rushed and opened the first one as soon as you found it, maybe the 2nd one would have been a better chest....

- learn about what the chest colors mean, and which ones to priortise over others.

- try to keep 1 key on you at all times. This will help when you enter certain rooms where you only have a short amount of time to react. ;)

- focus on rescuing NPCs first - either by following the "1 key at all times" mentality, or making sure you have enough money saved to buy a key

- if you get hit, don't panic! Panicking is how you get hit, and getting hit causes more panic. Just refocus your attention on your character and do the best you can to walk around bullets again.

- be wary of leaving valuable things behind... except for health >_>

Every run, every hit, every hand-sweaty encounter, is all just experience adding to the whole. Don't stress if you die, and take breaks if you find yourself agitated. Have fun!