RISK and BJ
There is NO "correct" answer as it all depends on multiple factors e.g. what spread you can get away with, the efficiency of your card counting system, penetration etc. BUT the major factor is called "Risk of Ruin" That is the % probability of playing and doubling your bankroll before you tap out, presuming that you play until one or the other occurs.
This is a "utility function" as it is known in economics and game theory.
It is drastically different for different peeps. If I am rich I may not care about losing. If I am anxious and have little discretionary funds so I cannot easily replenish a lost bankroll than I will want to accept very little risk.
I play a game similar to what you describe and I use a cash bankroll of $25,000
That provides me a very low "Risk of Ruin" betting from $25 to 3 hands of $100
If I attempted this with just $5,000 I would go belly up perhaps as often as 40% of the time.
The most common reason for novice Card Counters to go broke is their being under-capitalized.