There are some questions that you have to put to yourself:
1. What is the budget that you dispose of ?
2. Your current job requires a suit?
3. How do you feel in a jacket and tie, plus leather soled shoes?
Aside the case in which you suddenly dispose of a great quantity of money (lottery, inheritance, etc), a wardrobe change will cost you, so a certain amount of planning is necessary! Even with e-bay, sales, etc, you will need some budget to do that, and if you are a normal person, it will take some time.
First - buy the basics! If you need suits for the job go for 2 suits, each with 2 pairs of trousers - one gray, one navy (you will have a good rotation on trousers, which, from my experience are the part which gets more wear and tear). Buy the best quality you can afford, all year round. Do not invest in "brands", but try to find 1. the best fabric and 2. the best construction you can afford. Stay away from "great deals", there are always pitfalls.
If you do not need suits for your work, things are simpler (in a way) - you can get out with 2 sport coats and 4 pairs of trousers as foundation for your wardrobe, and that can include jeans (I know that some of our american colleagues wont be happy with that, but classic jeans can be smartened with a quality blazer and shirt). 2 flannels - mid-gray and charcoal, one chino, one jeans as "starter pack" for trousers, one very good quality navy blazer, one gray more coarse fabric (herringbone, tweedy, etc).
Shirts - again we go with the 2 case scenario - suit and sports. A minimal shirt wardrobe is half a dozen 6. If you go for the suit way you could do 3 whites, 3 blues (light to medium), french cuffs. If you go for blazers BD cotton oxfords are the best choice 3 blues, 1 pink, 1 white, 1 gingham (at least that will be my 1 week travel choice), barrel cuffs. Also buy the best you can afford, but the must is 100% cotton, no poly cotton mixes.
Shoes - 3 pairs 2 brown, 1 black, leather soled, goodyear welted. Styles, up to you, but the safest way is 1 black captoe oxford, 1 brown brogue, 1 derby. 2 belts, one black, one brown. The same - best quality that you can afford, and then take care of them (when you pay over 200 USD on a pair of shoes, you tend to be more careful with them). Wooden shoe trees are a must, good quality cream and wax also. Apply a conditioner after wearing them, put them on wooden shoe trees, let them rest, wax them before each wearing, 3-5 wears apply cream and re wax.
Ties - also 6 3 reds, 3 blue (they are the most versatile) 1 polka dot form each other, 1 repp from each other, 2 at your choice.
If you go on the french (double) cuff a dressy, but cheap, accessory are silk knots and barrels instead of cufflinks (if you read all the recommendations made until now, you are already spending a solid budget). Coordinate them with your ties.
If you wear eye glasses, one of your foremost concern is to be sure that you have a pair of extremely good looking eye glasses. I would say that must be your first priority.
Add to that some dressy socks (ladies love them) to complement your shoes, at least one cologne that fits you (good one, not supermarket brand), a good watch (vintage is a solution).
The comes the overcoat, gloves, head wear, scarfs, umbrellas, brief-case, luggage, shades.
A last piece of advice - the most important thing in a suit is FIT, not brand. So, try, take a lady friend with you when shopping (they have a good eye on details), find a good alterations tailor.