I echo all advice given by others: go with navy or charcoal, shoot for 100% wool, and try your absolutely best to get the shoulders right.
You may already have a decent sense of what a proper fit is for you, but I didn't back then so forgive the unsolicited advice if you don't need it.
First, go buy yourself a tailor's tape measure at the local fabric store so as to start understanding how wide the shoulders should be for you, seam-to-seam. Try on more expensive jackets to figure out what that width should be if you need to, then go looking for a less expensive suit that's as close to that magic number as possible. After you learn this measurement you'll start measuring all sorts of things in your closet, from sleeve length to tie width. My other advice in shoulders is to look for something less padded, but that all really depends on your build.
The other measurement that ranks high in importance would be the length of the jacket, since although a tailor can shorten it, accidentally throwing off the balance of the jacket is really easy to do if the bottom creeps up too close to the pockets. Everyone has a slightly different spot where they like their jacket to touch when holding their hands down at their side, but typically if you get close to your thumb knuckle you'll be ok. Anything too long and you're wearing your dad's suit; anything too short and you've blown, at minimum, the formality of the garment.
Nearly all other proportions of the jacket can be relatively cheaply dealt with by a tailor.
Finding a 36s (let alone a 34s, which is barely available at all, though at 150lbs I doubt that's really your size) is never that easy at most major american brands, and often they are still too big depending on your height. For something a bit more fashion-forward/euro-cut in that price range for a smaller person (I am one too), I would recommend looking at the following brands:
- H&M (like you said)
- Ben Sherman (can find on sale often - Nordstrom rack sometimes carries)
And then, possibly to the disapproval of others on this forum, I think you get a decent product and a great learning situation if you try out Indochino, the online made-to-measure company. Going through that process may not net you a perfect suit (only experience and money will get you that, anyway), but it will start to put you in the mindset of what really fits vs. what you'll settle for because it's "close enough" or "it fits ok for the price" -- just get ready to hate a lot of your clothes as soon as you are faced with what you sort of already knew - which is that very little of what you own actually fits.