I advise going with one of two formats, both using the same blind structure with 40% average blind increases. Try both, and see which your group prefers.
Format A is a 10-player T1000 tournament with no re-buys. This format offers good value for the entry fee, and stacks are deep enough that re-buys are not really needed. The tournament length varies from 4 hours to 8 hours (or longer), depending on how long you set the blind levels (15-minute levels = 4 hours, 30-minute levels = 8.0 hours).
Starting stacks
10 x T1
13 x T5
9 x T25
7 x T100
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39 chips = T1000 (250 big blinds with a 2/4 starting blind level). Use T100 chips for all color-ups (see below).
Format B is a 10-player T400 tournament with up to 15 total re-buys (that's all that your chip set will accommodate). Tournament length varies from 3.5 hours to 7 hours (or longer), depending on how long you set the blind levels (15-minute levels = 3.5 hours, 30-minute levels = 7.0 hours). Under normal conditions, expect to see about 25% re-buys.
Starting stacks
10 x T1
13 x T5
9 x T25
1 x T100
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33 chips = T400 (100 big blinds with a 2/4 starting blind level). Use T100 chips for all color-ups, and use 4 x T100 chips for each re-buy.
Blind structure:
lvl sb bb
L1 2 4
L2 3 6
L3 4 8
L4 6 12
L5 8 16
replace T1 chips with T100 chips (end of re-buy period, if used)
L6 10 20
L7 15 30
L8 20 40
L9 30 60
L10 40 80
replace T5 chips with T100 chips
L11 50 100
L12 75 150
L13 100 200 *** eot w/T400 stacks
L14 150 300
replace T25 chips with T100 chips
L15 200 400
L16 300 600 *** eot w/T1000 stacks
L17 400 800
L18 500 1000
Format A (T1000 stacks) will typically end no later than L16, while Format B (T400 stacks) will usually end no later than L13 (possibly L15, with 10 players and 100% re-buys). Allowing re-buys after L5 is rather pointless, as the re-buy stack size is only worth about 20 big blinds (or less).