You m ay want to get yourself a copy of "Gentleman's guide to grooming and style" by Bernhard Roetzel. It is good for a relatively new entrant and seems geared for the Teuton in all of us.

Ive seen a lot of bargains on Ebay.com and if you deal with the more reputable dealers (ie. thousands of transactions and a 99%+ rating) you should be OK. Ive seen shirts on Bromleys http://www.classicwardrobe.co.uk/-/Product-Type/-/Shirts.aspx which are well valued. I can say the Hilditch and Key are good quality and the sleeve lengths should be good for you. The English are helpful with size matters if you need to discuss it with them.

As for suits, I dont buy anything off the rack anymore and I am out of touch with what makes and models accomodate which types of bodies best. But maybe someone here or at www.styleforum.com knows. They seem to have younger and/or more budget conscience members who are generally congenial.

I think it's a good thing that you havent a lot of money to do the wrong thing with. This is a growth, experimental stage. You should spend more time researching and yearning. Style is as much in the mind as anywhere else. I sometimes miss the days when i had to make do with what I had. I felt I put more inventiveness into making it stylish. Enjoy this time, think about who you want to look like or want to be perceived as and you will develop a style. By the time youre making loads of money,  you will know exactly how you would like to adorn your person.

And welcome to the MB, I hope you find it exciting to indulge your every query or contribution concerning clothes. Remember that, wardrobe limitations notwithstanding, dandyism and the love of clothes is in the mind and that all dandies are equal.

Keep it simple and flexible.  A single-breasted blue blazer, grey trousers, and a white shirt and blue shirt can be part of your wardrobe foundation.  If I were forced to have just one item in my closet, it would be a blue blazer.  A pair of jeans and khakis would serve you well, which you can wear alone and with the blazer.  You can wear a nice blue blazer with jeans and be right at home anywhere in the world.