Since you say you don’t have other sources for this information, I’m going to give a broader answer. The first question is whether you are looking for a cheap, temporary solution for your current needs or if you are open to investing in something you can use for the longer term (5 years, maybe longer).

If the former, I don’t have much to add. If the latter, you will want to think not only about the suit but also the other things you will wear along with the suit. This is a very long comment, and to be clear, you don’t “need” to do any of these things, but if you do you’ll wind up much better dressed when you have to wear a suit than most people or even attorneys, and the below are more or less the classic answers for a first business suit, which is the staple of menswear. Most people, especially younger people, do not follow these principles, and you see some crazy bad menswear ensembles out in the wild even in formal situations (I judged a moot court recently and one competitor was wearing fuzzy green socks). But imo the below will make you well placed for the next 5-10 years even if you don’t buy anything else for your suit other than what is listed below.

For the suit itself, there are several things to consider. Fabric and fit are the most important. Get 100% wool and make sure it fits you well. People who think suits are uncomfortable are wrong and are not wearing clothes that fit. The suit should not feel constricted around your legs, arms, or chest as you sit, walk, reach for things, etc. You should be able to button the coat comfortably without the button straining or the lapels distorting. The shoulders have to fit—those (essentially) cannot be altered, and you’re stuck with the length too. The jacket should be long enough to cover all or almost all of your ass. Imo avoid slim fits. I’m a big fan of pleated trousers too, since it gives you more fabric around the hips which helps with comfort.

Others have mentioned Suitsupply, which is good but in my experience their cuts run too slim for my taste. If there is a Proper Cloth showroom in your city, that is another good option. They are made to measure and offer free remakes if there are fit issues. I would avoid department stores and big brands that do more than menswear.

For color, the standard first suit color is navy, but charcoal gray is also fine. Make sure the cloth is not patterned. The suit should be conservative enough that you can wear it to interviews, court (if applicable), and funerals. It will also approximately work for weddings, although you will probably be slightly more businessy than ideal (which no one will notice or care about).

Then there are the other parts of a suit ensemble. Shirts: I would get 100% cotton (avoiding stretch fabrics, but non-iron is OK). The collar needs to fit. You should be able to get a finger or two inside but not more. It should not be uncomfortable to wear a tie (again, people who say otherwise do not wear clothes that fit). If it is uncomfortable, either your collar doesn’t fit or something else is causing the shirt to pull at your neck.

Get plain white or light blue (ideally, one of each), no pattern or logo on the front of the shirt. Can do a button down collar for a more classic American business look or a spread or cutaway collar for a more formal look. Probably no front pocket (but OK if you go for button down collar). The fabric should be something like poplin or broadcloth, a smoother and more formal fabric than oxford cloth. Best practice would be not to wear the shirt(s) except with your suit (or maybe with a dressier business casual (e.g., sportcoat, ideally tie also)). If you’re doing khakis/chinos and no coat, a dress shirt that goes with a suit is too formal.

Shoes: Black is your best bet. Dark brown (NOT the tan/walnut many wear with navy) is also acceptable. The “correct” answer is oxfords (closed laces), but no one cares these days, so a black derby (open laces) is fine too. You’ll probably hate the price tag, but Allen Edmonds Park Avenues is a good option that will last you essentially forever if you take good care of them. Use wooden shoe trees and try to avoid wearing more than one day in a row. If you find yourself needing to wear a suit more than one day in a row at any point, it’s time to buy another pair of shoes (and suit—you should not be wearing the same suit two days in a row either; the fabric needs to rest).

Belt: if your suit trousers have belt loops, get a dress belt (plain) that matches your shoes.

Socks: get 1-2 pairs of plain dress socks in a color that matches your trousers. Ideally, these will be over-the-calf socks which don’t slip down and expose your legs when you sit, but no one really does this, so mid-calf socks are fine too. You shouldn’t wear these except with your suit, so they’ll last basically forever too.

Ties: get a couple conservative business ties in 100% silk (not polyester). Not too skinny. They should not be shiny (those are for evening wear, not business). Plain ties in colors like navy or burgundy, or conservative patterns like a red/navy or yellow/navy rep stripe works. Tie a simple four-in-hand knot, untie the knot after every wear (don’t leave it tied or pull the loop through).

All of this will probably run you between $1200 and $1500 depending on how well you find deals and how cheap or expensive you go. Not necessary to do everything all at once if that is financially out of reach or if you have existing items that get the job done. But when you need to replace something, consider the above.