Im curious if you have an updated letter of understanding or not (im not sure there is one) but....
After you get through the gaining process at your NOSC and do INDOC, you will start to drill at you unit. I would get one set of NWU type iii and some PTUs but nothing else. That is, unless your unit drills in khakis and you have easy access to a NAVY uniform shop. Buy the Black leather boots! (Basic, I4, or flight) Only Black is allowed at ODS - not brown. If you want to pay for 2 different boots then go for the brown, but leave em at home unless they change ODS requirements. I bought brown like everyone else in my unit - and then had to get black leather boots at ODS to wear for 4 days! I was a sailor that prepared for DCOIC and then had to go to ODS. I had all of my uniforms/seabag before I went (i wish i didnt). Remember, some of the active duty ppl you're there with may not even know what a US Navy is - ha - no uniform, no foundation. Go to ODS as soon as you can. Id say the earliest you could swing it is 6 months after commission. I have a lot of other ODS for reserve tips but that isnt what you asked
When i left ODS, DIVOLC was on my FITREP as completed and if not, many NOSCs offer DIVOLC over a weekend drill around the country. I havent heard of anyone going to IWBC for sure. NIOBC is for active duty but some reserve seats are available.
They claim it should look like this:
ODS first year 5 wks
RNIOBC 2nd year 5 wks
Phase II 3rd year 2 wks
But everyone is different. I did an AT before ODS and did another AT earlier this year before RNIOBC. Im not in the DC area where ENSs are running around everywhere!