Hi X-Check;
If you are doing a Battery Start (with APU bleed air, but no AC) then you won't be able to start ENG #2 first because the Isolation Valve will be closed (TRFR BUS #1 => AC) ... so start ENG #1 (recommended anyway). You will have bleed air to the #1 starter (APU Bleed Valve is on BAT BUS) and you can engage the starter (both Starter Valves are on BAT BUS)
No, you will only be able to engage the starter if the eng bleed is open, permitting air to flow to the starter.
Doing Bat start, no matter using APU bleed or gnd cart bleed air, if you don't have AC you can't move eng bleeds (so, you must left it open!). In the system schematic you'll see that, to reach the start valve air must flow thru eng bleed (going into the engine). That's why you couldn't start your "first" engine if the respective eng bleed was off.
After starting the first one, generator on bus, AC available and no problems to start the other engine (and now, with AC, no more BAT start - will have oil press, fuel flow etc).
Hope this clarifies, friend!
Cheers,
PP