Which start do you recommend for new players? I tried the Johnny one ("super hard") and ate shit. Not sure what I was expecting. Are the harder starts really challenging? I think I'd want a medium challenge, but the disparity between normal and hard starts seems quite huge, right?
Did you complete the tutorial? After that, next step up in difficulty is custom start > Easy difficulty. Normal start > simple difficulty follows.
You start the game with no recurring income and there are living expenses to pay every 10 days. If you can solve this then you have all the time you need to figure out the rest. You can control cashflow in two ways: minimize expenses and increase income.
Spending money can be a powerful accelerator for training in many ways. But a lot of things that you can spend money on are luxuries that you don't really need at the start. Two places where it is almost always worthwhile to spend money at game start are clothes and school. Wearing clothes appropriate for the activity give bonuses,
and some clothes also improve mood when worn. Since a bad mood can lead to negative effects that cost more sparks to manage, the right set of clothing can pay for itself.
Unless the slaver has A+ or S+ teaching skill, hiring tutors or sending the slave to school will advance skills faster,
and the slave will be less likely to refuse lessons. These costs are offset by reducing the time until you can sell the slave, which can result in a speed bonus (10$ per day) if you are completing a guild contract. A longer training period costs more due to cost of living - feeding the slave and yourself - as well as other reasons you may find to spend sparks.
Income comes from selling slaves or from winning events in the arena or from selling eggs/milk produced by slaves in your farm. The farm is an "extended rental" available from the real estate agency when you have an apartment (the Outcasts district apartment comes with one included at no additional charge). But slaves need to undergo surgery and recover from it before they start producing, and you need to feed them, so it's barely profitable until you have a fog fiend that produces cheap food for them. Keeping a fog fiend requires you to have a slave who can milk it, and that training requires high obedience. So at the beginning of the game, you need to sell slaves or win events in the arena. Living in the Slums while you're doing that will minimize your expenses, but will also make various aspects of the game more difficult.
Keep in mind that the guild gives you contract slaves for free but doesn't give you market price when you complete the contracts. You can get more income by paying for cheap slaves from the market and selling them to direct customers (or through the guild auction). However, you need to train them to at least D+ before anyone outside the guild will be interested, and you need to brand them yourself (tattoo brand costs money, fire brand requires you to pay for access to a dungeon) and ensure they have sufficient
charm to satisfy a buyer (aside from a few businesses that will buy slaves based on skills and rating only and don't care about charm). See the anatomy tab of a slave for more information on charm. Raising charm is another expense, but charm translates into more value from customers that care about it.
The guild will accept any slave that fulfills a contract; it doesn't have to be the one that they gave you. They also pay you more the sooner you complete a contract. If you think about these two facts, an income-maximizing strategy might occur to you.
Why do guild contracts at all if others pay more? Guild contracts give you a free slave of variable quality; some are very valuable (expensive to buy from the market). Raising your guild reputation also gives you access to more income from the arena by sending multiple slaves to compete in each event. But you can also raise your guild reputation by selling slaves in the guild auction, so contracts are entirely optional. They can be a source of cheap, valuable slaves and emergency funds (starting a contract gives you a prepayment).
The moneylender in the Slums is another option for emergency funds, but you have to pay back more than you borrow and there is a time limit. It has situational utility when you have insufficient funds to pay an end-of-decade bill. The clock starts when you take the loan...
Slaves with higher ratings are more valuable but take longer to train. However, the relationship between value and time is non-linear. Higher rating slaves don't take twice as long to train but can be more than twice as valuable. Therefore, unless the slave you are training would be extremely costly to train further, it's often better to continue training as long as you can. There's nothing that prevents you from training each and every slave you every train all the way up to S+ as long as you manage your cashflow well (though this requires you to make use of other sources of income like the arena and the farm).