Which one?
- Basic house upgrades to not lose stamina and NPC happiness?
- $300 for the yard defenses level 1 to penalize escape attemps and upgrading your captain's room so he is not bleeding happiness?
- Tuner and Valkyria being permanently missable?
- Pantry girl being your very first homeschooling priority to reduce ration cost for every single NPC in the house by 1?
- The basic pool ($7000 upgrade of a basic $15k Gazebo) so you can earn Affection +1 household-wide unconditionally + Happiness (via holding pool parties) so your janitors and maids don't hate you and increase disrepair in your house via sabotage?
- Unassigning followers when midnight hits so they are included in midnight calculations?
- Full House and Project Erebos taking days upon days upon days of training that is not worth the effort currently?
I think except for that last part, all of it are relevant to a new player. Even the $22k total pool is an investment into one of the best structures in the game. It's affection and happiness, household-wide (capped at Loving Affection and 100 Happiness) without any conditions attached except for actively holding the pool party itself (minor money cost and it needs to be held before 10pm). Especially for the male NPCs. You cannot fuck guys in your house. But you can hold pool parties (and arrange dinner events).
EDIT: To add for the pool, Truls overmatches most combat NPC options you have in the early game while costing $0 salary and he starts at Despising affection. Armand is tied for the best accountant in the game, he starts at a much higher Intelligence than Adrienne, and he has a propensity for leaving your house if he is unhappy (he is a servant; they can voluntarily leave your house in Conclude Day events). Cassius is hands down the best overall combat NPC in the game (at $0 salary no less) and he starts at Despising affection. Same deal with Aaron Kreuger, the best/second best melee combatant depending on his dice roll and training. Farming their affection slowly day by day is great. And the girls? Well, they have an aversion to putting their mouth or genitals anywhere near the same area code as your penis especially when your stats are low. Being able to passively farm their affection to Loving while you focus on one girl is very time efficient.