"bare minimum" doesn't really exist, especially if you have an actual problem you are trying to solve. Shocks/struts are the most likely culprit, so I guess that's technically the bare minimum. However, you will be removing a whole lot of parts along the way. Several of them are rubber (and therefore wear out) or fasteners (which rust). Everyone's judgement will be different regarding what items are "worth it" to replace "while you're in there."
I have done 3 complete suspension 'refresh' projects on my cars, and I have a pretty holistic approach. If it wears or rusts, and I can unbolt it, I will replace it. I go to
www.realoem.com, filter to my car, browse the 'suspension' sections, and make a list of all the part numbers. Using OE equipment can save a lot of money vs BMW-branded; most of the real stuff is actually Lemforder.
My wife's 2011 e90 335i xdrive is the most similar to your car (not identical, but close), and here is the list of all the parts I replaced. Do with it what you will regarding specific part pricing and ease of replacement.
• Rear Left Suspension
o Shock - BIL-24120395
o Upper shock mount kit - MON-907984
o Lower shock mount - LEM-3539801
o Lower shock mount bolt (qty 2) - BMW-33526764406
o Shock mount grommet - BMW-33506767010
o Bump stop support cup - BMW-33526764418
o Sway bar link - LEM-2993401 (33556764428)
o Upper rear control arm - LEM-3351801 (33322406292)
o Upper fwd control arm - LEM-3573301 (33322406289)
o Control arm bolts (qty 2) - BMW-07119906489
o Control arm “securing” (triangle) bolts (qty 2) - BMW-33306793891
o Control arm locking nut (qty 2) - BMW-33326760668
o Lower rear control arm - LEM-3067301 (33322406290)
• Rear Right Suspension
o Shock - BIL-24120395
o Upper shock mount kit - MON-907984
o Lower shock mount - LEM-3539801
o Lower shock mount bolt (qty 2) - BMW-33526764406
o Shock mount grommet - BMW-33506767010
o Bump stop support cup - BMW-33526764418
o Sway bar link - LEM-2993401 (33556764428)
o Upper rear control arm - LEM-3351801 (33322406292)
o Upper fwd control arm - LEM-3573401 (33322409890)
o Control arm bolts (qty 2) - BMW-07119906489
o Control arm “securing” (triangle) bolts (qty 2) - BMW-33306793891
o Control arm locking nut (qty 2) - BMW-33326760668
o Lower rear control arm - LEM-3067301 (33322406290)
• Front Left Suspension
o Strut - BIL-35142454
o Strut mount gasket - BMW-31306772226
o Upper coil spring shim - BMW-31336767500
o Lower coil spring shim - BMW-31336764372
o Strut mount - BMW-31306785962
o Sway bar link - LEM-3616501 (31356768771)
o Tie rod end - LEM-3388201 (32106793623)
o Fwd control arm - LEM-3711801 (31126768989)
o Rear control arm - LEM-3711901 (31126768983)
o Ball joint - LEM-3390201 (31126768988)
• Front Right Suspension
o Strut - BIL-35142461
o Strut mount gasket - BMW-31306772226
o Upper coil spring shim - BMW-31336767500
o Lower coil spring shim - BMW-31336764372
o Strut mount - BMW-31306785962
o Sway bar link - LEM-3616601 (31356768772)
o Tie rod end - LEM-3388301 (32106793624)
o Fwd control arm - LEM-3711801 (31126768989)
o Rear control arm - LEM-3712001 (31126768984)
o Ball joint - LEM-3390201 (31126768988)
• Other
o Front sway bar bushings (qty 2) - Rein 31356773512
o Rear sway bar bushings (qty 2) - Rein 33556761360