To be honest when creating dungeons I take into consideration a few factors :
Before considering these questions you want to look at the dungeon you have or haven't yet saved as if you were raiding it.
1. What is the default trap of the dungeon? The term ''default'' refers to the trap that will be disabled by Disable Potion without any deaths occurring. For this answer you can visit this excel page to find out for yourself : http://alexvdg.nl/kot/kot_bases.htmlIt is updated regularly. Also, there is a known trick that you can test in your own base which consists of stacking all 3 of your traps on top of each other and the one you will be able to move from the three is suposed to be the default trap. Except that that's been found to be false in some occurences; one of my accounts is currently in base 25 (1st trap set) and ingame it shows that the fly is the default trap. But, the default trap is the saw. The point is that you want your most important trap (the hardest trap to successfully pass) to not be the default trap or else your dungeon will suffer greatly from raids.
2. How effective is Gangup Potion in my dungeon? Ideally you'd want your traps to be set up in a way to negate gangup potion's effect. Many dungeons suffer from this potion when well used. In most dungeons you would use Gangup Potion to be able to get by the first few traps and then die in the last trap to then disable it with Dsable Potion. That's why having 1 really good trap and the two others traps decent is not ideal. The best way to counter this potion is to, like said in a previous reply, either move the door 1 square to the left and then test your base of simply do a mental simulation of what gangup would do. Obviously if you are not used to the game mechanics then imagining the results beforehand will not be as easy as just testing it.
3. Assuming that the raider will use Disable potion and die 7 times, will he be able to easily pass my dungeon? This question determines weather your base is a 0 star farming machine or a 1 star base with 5-10% chance of being robbed every time someone raids you. This also determines how confident you can be with your rituals. If you have a layout that will consistently get 0 starred even with potion used you can safely assume that you can perform a quite hefty rituel.
4. What set of trap offers the best dungeon I can possibly save? This helps you in numerous ways. If the set you are presented for the cheapest amout of gold consists of three traps that are low levels compared to other traps you own, you may want to check out the other trap sets to benefit from your higher level traps. Also, don't waste 150 orbs for the best defence (unless you are 100% certain it will benefit you enough to be worth 150 orbs) xD...
5. Can I save a dungeon that has 1 or 2 pixel jumps without any traps? The answer will usualy be no. But, if you can come by dungeons with gravity switches, planks or the trampolines, you will most likely be able to save layouts that provides 1 or 2 pixel jumps without any traps activated. Those dungeons are usualy the godliest of bases in the game due to their high resilience to potions. Disable and Gangup usualy doesn't do as well against those kinds of bases because it will be hard no matter what. Those bases are definitly worth spending alot of time saving a godly base. ☺
6. Considering how many teeths are left on my totem, is it worth saving a hard layout? This question is self explanatory; you don't want to spend a considerable amount of time saving a good base to then change dungeon the day after because you didn't notice there were only 2 teeths left. ☺
These key questions should enhance your dungeon's quality.
PS : Instead of searching on Kotdb or other sites for dungeons, lookup youtube channels of high level players such as bryan berndt, ash kot and others. Also, what I personally do alot is : I keep pictures in a folder of many godly layouts from players in the best guilds in the game : mishlo, syndicate and such. By going through all of their player's dungeons you can really pick up a good library of godly bases for your future bases.
I hope this helps,