Word Series- but it coments on Greek or Hebrew Text, use it all the Time
NICNT & NICOT- use this all the time
NIV Application Commentary (there is a podcast on this, good set useful for preaching) I have used some of these
New Internattional Greek-Comments on the Greek Text use it often
I have used several of the New American Volumes they are good.
BEC used severa of these, Luke is Excellent, Acts is good, 1 Peter is excellent, Revelation is good, have not used all of them.
I like technical stuff, you might not
Check out Best commenteries site.
What do you hope to get out of the commentaries?
If it's leading Bible studies, then Bible Speaks Today, NIV Application Commentaries are great
Are you Evangelical? I am, if are not then some of my stuff above may not apply
Do you want one Volume or multivolume?
You have 20 days. Look at the above site. Watch some of the podcasts as Dr J has done podcasts on the NIV app series, Expositors Series and may be others.
Do not be put off by some series saying they comment on the org. language; for instancs BEC usually translates and you can read around these things.
Leaving you in God's Care and Grace