Runes - runes are what you use to buy stuff and also level
When you die - you drop all your runes where you died. If you die again before gathering them up, you lose them permanently.
Runes are fairly easy to accrue if you don't mind grinding a little.
There is one spot in the game where about 30 mobs are that you can easily kill one at a time especially if you kill them from afar using magic or upgraded bows/crossbows. They each drop 1000 runes so I just go thru and kill them all in about 15 minutes or so and get easily 30000 runes.
You can also add another 20% if you get the 20% talisman and another 50% if you create an item that is really easy to make.
So you can get 1700 runes per kill.
The major bosses are a real pain. General Radahn is a nightmare boss. And the first boss to get into Stormveil I had a really difficult time killing.
The minor bosses - some are really difficult, some are not too bad.
I would level up to at minimum 50 before doing any boss though. Just my opinion. And level up even more for the more difficult bosses.
If you don't mind grinding, you can easily get to level 200 in a few weeks play. I just don't like grinding and am only at 163 after a few months of off and on play.
Edit - one other thing - once you kill the queen - she will allow you to reset your character if you don't like where you put your points into.
I have done it 3 times and I can do it another 6 times at the point that I am at.
Right now I am a spell caster but I might decide to go full out melee at some point.
Also - I only do major bosses when I have spent the majority of my runes because you might give up fighting a boss and decide to level up and you can't get your runes back from the fight against the major boss