What 3 companies should I buy If I want to be as accurate as possible?

[Ramm]

I'm not mentioning any specific countries and dates on purpose, If I can I hope to get a general answer.

THE PROBLEM: Time and time again I am faced with this horrible SPMBT problem as I'm sure some of you have also faced.
I go to the buy screen and I see light tank companies, heavy tank companies, mbt companies, RECON AFV/jeep companies, support infantry companies, normal infantry companies, etc. (The last two examples are the meat of my question).

I know that I (Lt. Col.) am in charge of 3 combat companies and myself (the invisible headquarters company)

When I buy my three Infantry companies for example do I buy one infantry RECON company, one infantry company, and one one heavy infantry support company or two infantry RECON and one infantry or three RECON or 3 infantry or 3 support? What should I do?

Please help me as this issue is really troubling me.
Any response at all is greatly appreciated
Sorry for the bad gramer I'm an American