Ainge (or for that matter any GM) will not spend on $$$ on bench players. You save your money for starters - and big money for All-Star starters.
The Celtics have very good bench players and a few that may be borderline the fourth or fifth starters on a playoff team. Ainge will not spend significant funds signing any of our players that are free agents.
He will save his cash to make a splash. The Crowders, Jerebkos etc.. can be obtained at any time. They are on rosters across the league and are easily obtainable. Teams like Cleveland, Chicago or Memphis will no doubt offer MLE to our free agents to fill their benches.
My thoughts on the C's roster
Bradley - couldnt stop Irving, still a solid defender, ultimately an undersized BENCH D+3 SG
Smart - still early in development - a rich man's Bradley.
IT4 - Bench sparkplug, undersized showed flaws against larger and physical opponents
Pressey - 3rd string PG
Young - not enough info
*Jerebko - decent bench player (#9-10 in rotation, not your first big off the bench)
*Datome - end of bench player
Babb - trade filler
*Crowder - energy, 3+D, solid bench player
Turner - inconsistent, borderline starter, effectiveness would diminish with a true PG playmaker
*Bass - borderline starter
Olynyk - bench stretch 4, needs to be more aggressive and gain strength
Sully - needs to get in shape, borderline starter
Zeller - solid #2 C
Wallace - expiring contract