The core statistics
VPIP is how often a player voluntarily puts money in preflop; PFR is how often they raise. A tight-aggressive regular shows a modest VPIP with PFR close behind it. A large gap between the two is the signature of a calling station, and it is the single most exploitable pattern in low-stakes poker.
Add three-bet percentage and fold-to-three-bet and you can construct a preflop plan against almost anyone. A player who three-bets rarely and folds to three-bets often can be attacked relentlessly, and no further statistics are required to know it.