Its really tough to predict who will be available at this point, using Draftexpress as a mock and my tiers(
http://www.celticsblog.com/2015/3/18/8241001/tiers-of-an-nba-draft-addict )I would do the following
#15 Poeltl (DX has him going 14 so this may require using a 2nd [#43] and $$ to trade up a spot). This pick is actually against my tiers but his potential and position make a stretch worth the shot. Looney or M Pope are also options but both are higher risk then Poetlt. If it wasn't for KO and Sully being on the roster the safe pick at this spot would be Harrell. He will be a very solid pro and provide toughness and D at the 4 where ever he is drafted.
#26 Hollis-Jefferson (DX has him going 24 but it would be well worth it to trade #33 to move up). He has a lot to work on but his athleticism and D are elite thats a great starting point.
If not traded, Euro stash will be likely but if the Cs stay domestic
#33 D Johnson, if he was on a different team I think his stats would make him a late teens pick. Worth a shot in the 2nd.
#43 Ron Baker, has a great skill set to make it as a role player