Not all teams will be buyers. Some teams will be using much of their space to retain top players.
I've tried to form a rough list of cap space teams will have but it's not 100% accurate due to cap holds which can change.
ACTIVE
RANK TEAM PLAYERS GUARDS CAP FORWARDS CAP CENTERS CAP TOTAL CAP Cap Space
1 Philadelphia 76ers 11 $4,171,689 $6,489,583 $8,084,760 31,927,380 $34,572,620
2 Portland Trail Blazers 8 $17,629,187 $12,235,750 $8,091,879 37,956,816 $32,310,074
3 Detroit Pistons 10 $18,351,316 $11,108,458 $3,272,090 39,488,010 $27,011,990
4 New York Knicks 5 $9,552,391 $23,720,059 $0 39,601,427 $26,898,573
5 Atlanta Hawks 9 $18,196,733 $10,027,088 $12,000,000 40,223,821 $24,715,679
6 San Antonio Spurs 6 $17,016,447 $2,328,664 $16,000,000 42,425,096 $24,074,904
7 Dallas Mavericks 7 $16,723,759 $25,640,495 $0 43,906,698 $22,593,302
8 Phoenix Suns 9 $21,412,600 $17,211,545 $3,807,120 47,999,723 $18,500,277
9 Los Angeles Lakers 10 $31,909,287 $6,802,151 $9,981,348 48,692,786 $17,807,214
10 Boston Celtics 10 $20,771,362 $15,800,625 $4,782,135 41,354,122 $14,557,030