What regulation specifically talks about ordering and approving the funding for initial dress blues for long term SM?

Initial issue only applies to when you initially join. Service members are responsible for purchasing and replacing their own uniforms.
If you look at the fielding initiatives when these items are introduced, they explain that the clothing items are gradually phased in over years to allow SMs to save and purchase the items on their own. The guidance is that you receive a clothing allowance every year and that is used to buy a piece of your ASU's every year.

Someone will be along to correct me if I am wrong but the old DRESS BLUE uniform is gone (You can wear it if Retired along with Dress Greens) , What they have now is the Army Service uniform (ASU) which is blue, The class B version with the shirt and long/short Sleeve shirts that are issue , the MESS BLUE uniform and the Mess Whites (You Buy) . If I recall correctly the only Soldiers that were issued DRESS BLUES were old guard back in the day. If you were/Are in the Reserve you should have been issued them from Supply since you don't get a uniform allowance. See your supply folks and work the issue. I just broke down and bought the Class B's to attend my sons Infantry graduation and I bough MESS Blues a good while back for dinning In/Out.

New troops- clothing bag issue. Troops with more than 2yr in (think) yearly Clothing Allowance. I believe you are talking ASU. Dress Blues are not issued, optional uniform you buy them.