Gems are the estate currency
Several Blue Prince rooms list a Gem Cost in their data. Gems pay for the expensive parts of a run, and a run stalls the moment the gem pool dries up. That makes gem rooms the quiet backbone of any deep attempt.
Balancing spend and income
Draft an income room before you stack high-cost rooms. A single gem room early pays for several later placements; skipping it forces you to avoid the rooms you most want.
Reading gem cost
In the room database, rooms that list a Gem Cost show it on the card. Use it to spot which rooms are cheap fillers and which need an economy behind them.
When gems run low
If the pool is thin, prioritise rooms that give gems or steps over flavour rooms. A shorter but funded route beats an ambitious one that collapses at room 30.