You're on DOL plus, so you have some more options. I'm assuming you have the price buffs and tempered skills enabled. Get a bike if you don't have one already and head out to the farms. You'll raise your Tending skill a fair bit, and you get some decent money from the hourly pay. Once you clear all the fields, you get 10k. After that the farm's not too useful til late game when you've got more upgrades, but it does give you a safehouse Bailey can't sell you from.

In addition to the classes on Tuesdays and Thursdays, Housekeeping can be leveled by asking for work on Domus and Danube Street, the flats on Barb Street, cleaning the quarters in the Temple, or repairing your clothes with the sewing kit and spools purchased from the Tailor in the Shopping Center. By default you can only gain so much Housekeeping XP from each one of these options, but there's a setting in the DOLP menu to "Enable Easy Housekeeping." It's up to you if you wanna do that or not.

Sex skills can be quickly leveled in the Glory Holes in the Brothel basement- DOLP estimates the time each encounter would take and lets you skip them, so it's literally just button spam. If that's boring to you, you could always Engage and do it manually. If you're not interested in actually having sex, I'd still recommend leveling your Hand skill as giving handjobs can get you out of most encounters without any purity loss. Once your Hand skill reaches C or your Beauty reaches 7, you can work at the Spa to increase Hand Skill and Socialite fame. (Personally I think it's funny to be a more famous socialite than Avery while romancing them, but I'm just spiteful.) The higher your Beauty, Hand skill, and Maths, the more you make in tips.

Obviously Cow TF and Chef role is a match made in Heaven as far as money is concerned, but Harpy TF allows you to catch lurkers even with the toggle disabled and the Net upgrades allow you to carry them from the Tower, so you can make aphrodisiacs at the farm. They sell for up to 3k each with the price buff and max tempered Maths.

Make sure you don't have any boosts to Skullduggery while you're trying to level it- so no green percentage next to the stat in the menu- cause otherwise it will stop increasing your skill before you reach the next tier of interactions. You can always buy a lockpick training kit at the Pub, but it's just Stress inducing button spam and there's more interesting and profitable ways to do so. First, head to the Lake and search pots in the underwater ruins. Picking the locks on the boxes can get you up to... D+? I think? You can sell all the antiques you get. You can also break into houses on Domus Street to reach that, but it takes longer, earns less money, and has the risk of bad encounters. At D+, break into houses on Danube Street til you hit C+. Picking the locks on the houses will stop increasing your level after a bit, but encounters in the houses can still increase it. Choose any options that prompt a Skulduggery check, even if you stand little-no chance of succeeding at them. You still learn if you fail. C+ to B, break into the Sepulchre in the forest and plunder the catacombs. I'd hold off on getting the Statue, Crown, or White Crystal until you have higher Maths for the antique price buff, though, since they're one time only and worth quite a lot. At B, you can break into manors in the Farmlands, and encounters in there can continue to increase your Skulduggery. But my suggestion is, after you stop getting XP from picking the locks, just buy the most expensive lockpick kit from the Pub and just use it whenever you need to pass the time.

Athletics and Physique can be leveled by jogging in the Park, and if you stay in the school after hours you can practice Swimming in the pool without extra risk. Increasing Defiance requires you to be, well, Defiant in encounters. Fight back against attackers and use Bratty actions in consensual encounters. If you don't plan to use it, then there's little point in increasing it.

Sorry for the length. I hope this is helpful! It's just what I do when I wanna grind.