DenizenKane wrote:What kind of effects should I avoid?
What's your core adventure structure? What effects break it? If the main thing your players do is a wilderness adventure followed by a dungeon crawl, then:
Flight beats almost every wilderness challenge and many dungeon challenges.
Short-range LOS-limited teleportation beats some wilderness challenges and many dungeon challenges.
Long LOS-limited teleportation beats almost every wilderness challenge and the same dungeon challenges as short-range does.
Burrowing beats most wilderness challenges and some entire dungeons.
Walking through walls and short-range unlimited teleportation beat huge numbers of dungeon challenges.
Long-range unlimited teleportation beats dungeons entirely.
In terms of combat, all of these apply for avoiding monsters that can't do the same thing. If you actually need to kill the monster, they're only relevant if they allow a you-can't-get-me kiting strategy.
And you don't need to avoid these effects, you just need to postpone them until you've gotten enough mileage out of the things they automatically beat.
DenizenKane wrote:How do you handle the parts of the game that dont work? Like Stealth, Diplomacy, Illusion, Kingdom Management?
Respectively: handwaving, magical tea party, Silent Image is holograms, and I'd need to write a homebrew system for that when it came up.
Mind caulk is problem for a system - if the rules are unclear or janky enough that each DM comes up with their own ting, then whatever fun you have with those rules is actually the DM's work and not the system's. But as an individual DM and not a system writer, whatever works for you is fine.
DenizenKane wrote:How far can you go before you might aswell write another monster manual?
You don't need to write a monster manual as an individual DM. 3E's CR system is inaccurate enough that you'll have to be fudging things and checking for gotchas no matter what you do with it; this is just part of DMing a 3E campaign.