So nobody's interested in playing a succession fortress. That's fine.
I've been using the duel arena and maging away in the friendly world (40) for a while, and what will follow is a poorly disguised rant. Here is a list of what my rules would be if I could somehow enforce them.
First, if you've come to the friendly world, don't expect people to stake. If you are staking, it should be the sort of stake people might make once in a while, like something below 1m. Don't offer lots of staked duels, as that's not what I'm here for.
Second, don't randomly yell 'funning'. This is the 'funning' world and we're all at the duel arena, it should be blindingly obvious that we are all 'funning'.
Third, don't put up pointless rules: 'no drinks, no food, no prayer'. I agree, people using food is silly, boring, and pointless. The same is largely true for protection prayers, unless someone's obviously outmatched and could do with the advantage. But putting these strictures in place slows everybody down for the sake of one or two food eaters. Just ignore them, don't challenge them again, and move on. It would save us all a lot of time if people didn't put up these unecessary rules.
Fourth, don't shout 'owning all' if you immediately put up some sort of weird ruleset (no hats and boots! melee only!). Of course you're winning if you disable every way you could possibly lose, but that's not skilful, and it doesn't give you the right to act as if you're some sort of superb duellist: you're just an annoying rule-setter.
Fifth, don't stand there and shout for people to challenge you. If you want some duels, people might challenge you, but unless you fit into a rather specific class or level set, you're much better off challenging lots of different people in the crowd. Challenge people and look for a more likely to accept opponent, and keep challenging more and more likely people until one accepts.
Sixth, and this is more of a tip than a rule, offer rematches if you might win. People will often accept, and it gives everyone a chance to prove themselves.
Seventh, be polite. Accept a fight as a true contest of skill and stats. We all have lag sometimes, but this doesn't mean you should tell people to 'gtfo' if they say 'good fighting'. Equally, there's no need to exclaim 'well **** my uncle!' after you've finally won. It's crude and therefore irritating.
Eighth, give and take. We can't always win, and we can't always pick winning duels. If you're not getting any challenges accepted and someone who will probably win does challenge you, there's no need to turn it down. If we all let each other win, we'd all get fancy hats faster, and that's a good thing. It won't devalue your acheivement that much, and it will make things more pleasant.
Ninth, give each other advice. If they're missing something out, if they can't understand something, whatever: help them out. It won't hurt you that much, and it will make the whole thing a lot more fun.
Tenth, don't be deceitful. Perhaps you're clearly wearing a hybrid outfit, like void, and that's fine. But don't deliberately have a special outfit you wear to get challenges, and then change into something much more powerful when you're in the arena. Wear what you actually fight in, so we know what we're up against. Obviously if you're hybridding this doesn't apply so much.
Eleventh, unsheathe your weapon. It tells people your combat level, which is an important way of knowing whether they should challenge you.
If people followed these rules, the arena would be more fun. We also might get duellist's cap upgrades slightly faster, which would also be good. I hope you find them useful. There are 11 rules because Saradomin, Guthix, Zamorak, Bandos, Armadyl, Zaros, Seren, Brassica Prime, Marimbo, and the 2 Pantheons makes 11 broad collective groups of religious followers. Actually, I just rambled until I hit 10, then remembered sheathing.
Bandos is to Zamorak as Zaros is to Saradomin: a heightening of the concept. Armadyl's an old fool. Just a (poor) theory.