First things first OP, it’s always a good idea to ask questions when you are confused. Trust me, something will always confuse you in this game, even once you do internalize all of this knowledge.
Secondly, I would suggest starting your journey to buildmaking with this All VH Formulas - Google Docs. It and the other sources linked with it exlplain just about the entirety of the Borderlands 3 damage formula. It is a lot to take in, so take your time reading through them and ask questions whenever you feel confused about anything.
So to your questions
All I can suggest is saving DLC 2 for when you are level 72 since you get a very powerful artifact (the Pearl of Ineffable Knowledge) that you can only get once on completion of a quest in that DLC. Otherwise, do them in whatever order whenever you want. They are all fun, and for endgame activities each has a use.
- Scraptrap farming for easy XP in DLC 1
- Ruiner Farming for a good combo of vault card XP, Guardian Rank XP, and eridium
- DLC for testing builds against Psychoreaver and Spongeboss
Do you feel like you want more of a challenge beyond where you’re at right now? If so, turn the mayhem up until you feel comfortable. If not, stay on M0. I would further suggest not going beyond M4 until you hit level 72 if it’s your first playthrough.
Bloody Harvest, Valentine Massacre, and Revenge of the Cartels were seasonal events that were made permanent. They basically entail killing special spawns to unlock a portal to go to a map where you do a dungeon run, defeat a boss, and get special loot. The events make the game more difficult by adding more spawns, and drop some nice gear. Most people like having Cartels on, but Bloody Harvest has it’s own special anointments that just rad.
To keep things simple, go with the first one. It has much better gear imo.
There is no difference between TVHM and normal mode once you turn on mayhem. It’s just a way to replay the story with scaling enemies. You don’t need to ever touch it.
Do arms race if you like it, don’t if you don’t. Takedowns should wait until you have a good build put together to clear it well. They can be very frustrating without a build strong enough to handle them.
Yes, it is all of those. While some abilities mayhem scale and can get away with less investment to be usable at M10, most guns need a supporting build, somewhat decent gear passives, and decent anoints to perform well.
M10 came out 2 level caps after the level 50 cap, it was not designed with your current level in mind. If you were at level 57 with a somewhat finalized build, it would be significantly easier since the content has gotten easier over time.
If you have a gun with the “on action skill end, deal 50% additional damage as fire” on your shield and grenade, one of those will not apply. However, if you had one anoint dealing 50% as fire and one doing 50% as shock, those would both apply. There are very few anoints that can even have the opportunity to roll on multiple slots and stack, and there are only 2 or 3 that actually do (Amara’s Bloody Harvest specific anoint : terorr skulls).
As Amara, you typically want gun damage anointments when using guns instead of bonus elements. She doesn’t have a lot of that stat, so using things like Consecutive Hits, Kill Stack, or Phasecast 250 really help her damage output.
If you can’t clear M10 efficiently, it won’t be fast. Just turn up the mayhem to whatever the highest level you can comfortably handle is (I suggest Mayhem 4, because we were all using non-scaling gear in that mode before M2.0).
I know this isn’t super comprehensive, but it will be much easier to answer specific questions than try to give a general rundown. If there is anything in this post that confused you, please let me know and I’ll do my best to explain it.