M.P.
I'm lactose intolerant and use rice milk in everything that calls for milk.
I've done an elimination diet twice. Both times I started with rice and lamb for 1-2 weeks. Sorry I can't remember how long. Probably because I got such a terrific headache both times that I quit. The idea from there was to add one new food/week and keep a diary of my body's reaction.
I started with rice/lamb because rice is rarely an allergen and lamb because I hadn't eaten very much of it. My doctor preferred that I start only with rice but my system does not do well without some protein.