How about a place like Godfry's (http://www.godfrys.com/suits-sportcoats/). They have a wide range of brands for you to try, and you can get a good idea of what looks good on you and what you prefer. When you go to a tailor re. alterations - make sure it is someone who knows what they are doing, and allow them to educate you, rather than trying to spell everything out from things you've looked up on the internet or had us answer here.
Styleforum, and frankly, any internet site, is good for getting started on, for finding out bits and pieces of information, and to discuss a fun subject with fellow enthusiasts, but having someone really guide you through things in real life is invaluable, as is experience.
One thing that I would suggest for sure - for your first suit, get something in standard navy or charcoal, that has a fairly standard cut, and work up from there. Do not skimp on the price, but don't splurge either. There will be time for splurging and for saving when you have more experience, deeper knowledge, and a strong understanding of your personal style.