i´d take at least a 34.9 for the top tube,a 38 for the downtube,for the cs and ss its common to use something between 12 and 21 mm(edit:or even tapered,better for the rear dropout join to fit those thingies of the dropouts that sit in the stays tubes),so youre pretty free in choice there.you could use higher diameter ones for the cs and ovalize them at the bb to gain space for the sprocket and tyre,and at the dropouts to,well to weld them on without having no welding surface at all.seat tubes hmmm,a 25,4 inner would be 26 outer dia,so its a thing of choice for the seat post dia,if you build seatless,its unimportant,but under 26 youl end up with less seatstay welds,making it weaker.
thats so far what i can tell on the tubes,josh can give more precise info for sure