The Ranger
Lots of people have written lots of words arguing about the balance and flavor of this class. I think it is more balanced than some people believe, but I do add the following house rules that give small buffs to the ranger:
- Attacks against the ranger's favored enemy score a critical hit on a roll of 19. Reasoning: favored enemy doesn't provide any combat bonus, which feels odd, and this change is minor enough that it shouldn't unbalance anything
- Primeval Awareness doesn't expend a spell slot. Instead, it's usable once per short rest. Reasoning: This feature isn't really that useful, I never felt like it was worth losing a spell slot for
- The beastmaster's companion gains proficiency in Wisdom saving throws. The ranger can spend her own hit dice during a short rest to heal her beast. (Also, the beast makes death saving throws: I think most DMs would do this anyways as it certainly counts as "a particularly important NPC" but it's not explicitly spelled out in the rules so I might as well mention it.) Reasoning: Animal buddy is a bit too squishy at higher levels, this makes it harder to kill
I have played with these rules in my home campaign, which has a beastmaster PC, for a while and haven't felt that there were any issues with them, but am open to discussion if anyone has a particular opinion about them.
Knowing Stuff
A lot of times people are in combat and they ask "Can I roll an Intelligence check to see if I know anything about (the enemy)?" so they can get some idea about its weaknesses. There are no rules about this but usually I make this take a bonus action or a reaction (rather than just being a free action) depending on if it's your turn, because I feel like it takes a few moments of focus to try and recall information.
Spell Scrolls
You can attempt to use a spell scroll even if it's not on your class's spell list, as long as you have the ability to cast spells (as a class feature or feat; can't be through innate racial spellcasting). You do so by making an Arcana check with a DC of 10+the spell's level, but if it's not on your spell list, this check is made at disadvantage.
Interludes
Shamelessly stolen from Savage Worlds. This is another thing I've been using in my home campaign but I think it'll work in PbP as well.
During a short rest (or long rest / downtime / other appropriate break in the action) a character can choose to spend some time talking to their companions. They tell a story about an event from their past, and gain a point of inspiration. It doesn't have to be too long, but it should add something new to what we know about the character.
I like this because it encourages RP and building character relationships. A lot of times, someone has a backstory fleshed out but it never really comes up in game. Also, I always forget to give out inspiration for good roleplaying like I'm supposed to, so it helps make sure that I actually use that feature of 5e.