There are a lot of skills and spells you can train as you progress, each of which costs money. When you can afford to, you should train all the abilities that your class trainer offers. If you're completely broke, it's fine to put off upgrading abilities you rarely use for a level or two so that you can upgrade your most-used abilities. If this happens, you should ask yourself whether you are spending too much money on buying unnecessary equipment upgrades or leveling production trade skills. Be sure to save enough for class abilities and riding training before spending money on other things. This assumes you're earning money at a rate where buying skills makes a difference at all. If you have a hundred gold from two gathering professions by level 20, those skill ranks costing a fraction of a gold won't make any difference to your purse.
For the duration of the fight, creatures in the immediate area will not be visible to you (but they may still attack you if they wander too close). Keep in mind that other players will still be able to see you and attack you if you are eligible for player vs. player (PVP). Other players will also be able to view your pet battle in real time, including the pets involved as well as their health as the match progresses.
An important aspect to crafting professions in BfA are the warfront contributions. During the contribution phase of a war front you will have to turn in various crafted items to help the war effort. During this time you can make gold with all the professions in the game if you are crafting the items that are currently required for turn-ins. This effect is pretty much the same across all the professions, so I will not be mentioning it specifically.
Some quests in my guide are marked as "SKIP" and colored in red. These quests are simply either too hard to solo or not worth the XP/time and are skipped. My guide will only list SKIPPED quests if the quest is a direct follow up after completing a quest, not one that you have to click the NPC again to get it. If you hover over the skipped quests, it will give info on why it is skipped in the guide (unless that info is already listed directly in the guide text).
Chilled to the Bone, Dampened Magic, Kleptomania, Netherwind Armor, Prismatic Cloak, and Temporal Shield have limited use in PvE content in terms of increasing your damage in the open world, but they can be situationally useful. Notably Temporal Shield can be utilized for, functionally, an extra 6 seconds of combat time against large elite mobs.
Formerly, when you visited a new zone, you would be very careful, tiptoeing around, cause everything was higher level than you. But as you dinged (leveled up), you would get more powerful relative to the locals. So you would feel more confident and capable. Dinging came to represent more HP, more Mana, better hit ratio, more crits, more talent points. you felt REALLY good when you dinged, like you had accomplished something. Almost tangible. You would think "now I can go back and take that mob/group that ganked me". And then when you had done all the quests, you would move to another zone and do it again. Fun!