The ideal buy for UK1 is 3 inf, 1 carrier, 1 destroyer. This creates a UK navy round 1 that can start trading with Germany round 2. If this is not possible, 3 units and fighters. Always buy 3 land units in India if at all possible. This priority is above even creating a UK navy.
A key point about defending India is that UK fighters should be sent within reach of landing in India round 3. Ideally landing West Russia round 2. With 3 purchases in india Round 1-3 and all available fighters arriving in india, Allies can usually hold.
Hit sz61 with a fighter and cruiser. All other exchanges in the Pacific are unfavorable round 1. Better to wait until round 3 when US fleet is in Pacific (assuming it’s a KJF). Uk can either merge with USA fleet or trade east Indies round 3.