A GUIDE FOR PLAYERS WHO LIKE TO ADVANCE IN THE GAME WITH INSANE SPEED BUT NOT USE BUGGY OR OTHER "CHEATS"
This guide is written to get you as much money and xp as quickly as possible. It's also useful for rapid access to tfs, arcane points, etc.
STARTING CHOICES
Best starting background for new players = Soldier due to the very significant combat bonuses it gives. These not only help early on but they also scale up with level. However Teacher, Butler/Maid, Muscian, Student, and others can also be good. No other starting game choices except your background really matter much, with the sole exception of whether or not you want to start as a virgin (recommended).
LEVEL UP & GEAR GUIDE
STAGE ONE: 0-5 ish
Run the easy, no-combat errand quests and hit a few low level goons in alley ways to get early xp. up to at least about 4 or 5. You can find some decent gear on low level goons, with my favorite being a kerambit. Gear up in whatever you can find at this point.
Try to get your physical prowess to 36 early so that you get the bonuses from that. You can pick up extra physical prowess points not just from perks but from fetishes too such as self-denial, dom-sub switch, and a few others. Prioritize any fetishes that offer combat bonuses like this.
Get the "orgasmic level drain" perk. Make sure that it stays off most of the time, but turn it on immediately at the completion of each combat for ... well, you'll figure it out.
STAGE TWO: 6-15 ish
As soon as you can, by level 4 or 5 certainly, buy a slave collar or enchant any item with the "enslaves" property. If you're short on money because you just got your slaver licence, then make an item instead of buying the collar.
Go to one of the purple "dangerous" back alleys, and meet your first incubus/succubus. Defeat them in combat and use orgasmic level drain to suck out and take all of their levels. This will rocket you through a few levels. Then put the slave collar or item on them. Go to the slave market. Use the management screen to remove the item from them. Then sell them off for 50k+. Use that money to buy a few more collars. Wash, rinse, repeat. You may actually want to keep one of the succubi as your slave and drag them along exploring with you to level them up.
GEAR
Now you're probably around the mid teens with maybe 250k- 500k or so in the bank and lots of perks. Do Nyan's supply chain quest. Use your money to buy up decent gear, and take the perks that allow you to equip it. Basic gear includes the brilliant scientist set, milkmaid set, rainbow set, and cattle set. I mention these sets because they seem to offer the best combination of stat points and set bonuses, they can all be worn in combination, and they can all be bought in the stores. You can round these out with a couple of the enforcer set items covering slots you don't already use. My favored weapons are the purple or gold feathers (get 4 arms and use one of each color) or a zweihander for rapid fight ending. Other combinations are fine too though such as the katana/wakizashi, the male and female japanese sets, the frost/fire jewelry, the sadomasochist collar, or etc. If you're a primarily physical-only combatant or if you've got the maid/butler origin, then you may want the butler or french maid set.
Buying up just enough spells to get the bonuses from those is also very good. The water-based healing spell and the arcane spell allowing telepathic suggestion is very useful. The latter saves you lots of time and arcane energy, and the latter allows a variety of both combat and sex benefits I won't go into (because this is just a rapid level guide).
You can intersperse these xp and money/slave runs with the enforcer quest and the harpy nest quests and other quests in Dominion if you want, but that's not strictly necessary.
STAGE THREE: 16-25 ish
Go down into the bat caves and repeat what you did in the back alleys except against bats and slimes instead of demons. The NPCS here are 10-12, not 5-6, so you'll be able to suck out a lot more levels. You'll also be able to grab slime tfs which you can later use for transforming yourself and others into almost anything you want. You'll be coming out of the bat caves after several combats at maybe around 20-25 or so, depending on persistence. Instead of just draining everything down there you may want to pick one of the earliest you find, enslave them, and drag them around with you for leveling them up.
You can do the slime queen quest around this time too if you want, or just after completing most of these bat cave runs.
Perk up your arcane just enough to be able to summon an elemental. I think you'll need it at least around 35 arcane and 300 mana. Pick any elemental you want. I prefer fire but also arcane is good too. Summon one elemental. Use your phat piles of cash to buy basic gear for them as mentioned above.
STAGE FOUR: 26-35 ish and beyond
Go into the imp tunnels and start doing to them what you did in the alleyways and bat caves. Suck out every last bit of that sweet, sweet demonic energy, beginning with the highest level imps each time. Make sure that you bring a follower to level up with you. You'll come out of it in the mid 30's at least, and much more if you're persistent. If you don't have a permanent follower yet you'll need to get one at this time. Get the highest level imp you can if you don't already have a follower. Anything will do. Keep in mind that the more followers you have and the less both you and they are transformed the more tf potions the imps will drop. These are good both for cash and because, hey, tf potions.
STAGE FIVE: 36 and beyond, the Central Citadel challenge, flavor quest wrap up, choice to become a demon or not, etc.
Go trash the central citadel in submission with your elemental and follower both in tow so that all of you get the special perk you can only get from this fight.
Decide if you want to transform into a demon.
Wrap up any remaining flavor and relationship quests you haven't done.
PASSIVE MONEY GUIDE
The best way to have continuous cash flow, so that you no longer need to worry about picking up every spare coin or selling slaves, is to build a dairy chamber and use your water-based free fluid enchantment ability to turn your slaves into cum and milk gushing futa supercows. Each one can make up to 30k crowns a day if they produce gallons every hour. Make sure that they have at least the lactation fetish ... they'll thank you for it.
FOLLOWER GUIDE
If you don't care much about your follower that's fine. But if you do then here are some ideas about optimizing them, or the pros and cons of each. Demons and imps are good because you don't have to worry about wasting tfs on them, but it's also a one-way ticket because any offspring they produce will be at least half-demonic, and those of imps will always be only imps. Half-demons are good because they have some of the best stat bonuses, and you don't have to waste tfs. They're my favorite overall but they're practically nonexistent unless you produce them with a demon and meet them as your own offspring. All other races are OK and you just have to pick which you like best, which gives you the racial bonuses you want. I like rabbits. The advantage of non-demonic races is that, although their racial bonuses tend to be inferior, you can change them at will with slime or other tfs, and you're not locked into demonic offspring.