Xibei San Ma
For a micro power, Bhutan is as good as any. An outdated army, not much IC or resources, little room to expand. But being a puppet of the UK has its perks, and there are some options to go for if you're looking to expand.
One research slot, one tech team. Even worse, it's terrible at industrial techs and not exactly top notch at infantry either. However it does do land doctrines well (as well as you can expect from a skill level 1 team, at least), and if you plan to stick with the UK (or ally with Japan later on) then it's best to go for Grand Battle Plan. You start with no industrial or doctrine techs at all, and great war equipment for your troops.
Bhutan starts as a puppet to the UK, and thus is a part of the allies. Interesting options later on include going with Japan (if you want to grab parts of India) or even try to get something going with the USSR. Being a paternal autocrat could help if you want to ally with Germany, but they won't be sending you any help and it generally is a terrible idea. Overall, you won't be having the kind of money to turn bad relations good, so sticking with the UK is a good, albeit boring, plan.
You start with 5 IC, and a surplus of energy and metal barely worth mentioning. If you want to trade, you'll have to use the little money gained from being locked into a high consumer goods production or use IC to make supplies.
You might have a little extra cash, but nowhere near the amount you need to get useful results out of spying. Get your blueprints from the UK instead.
You start with two 1918 infantry divisions, and with a manpower growth of 6.4 per year there's not much you can do about that. After a couple years of IC and manpower techs you'll be able to field an army of a few infantry divisions and some milita. A navy and an air force is pretty much out of the question. You don't have any coast, no air field, and not the means to produce anything capable of hurting anyone. World conquest material, it ain't.
Build up, go for Tibet (which is as weak as you, but without any allies) and prepare to fight the Japs, or wait for the Japanese to make a push for India, ally with them and start grabbing provinces. There's plenty of resources to the south, and IC to the west and east. Annexing Nepal is a must, and the manpower in Lucknow would certainly be welcome. All in all, a successful alliance with Japan could triple your IC, manpower and resources.