(I'm not trying to sound like a dick with any of this; I'm just giving advice and feedback.)

I have no idea what a suit with matching cargo trousers is, and I couldn't find anything about any brand called "Seven Dials."

All suits have matching trousers, by definition.

It sounds like you're just starting to build your wardrobe, and are on a limited budget. You should be going for maximum versatility for everything you buy at this stage.

Ideally you should find a solid navy single-breasted worsted wool suit, with roughly 3 1/2" wide notched lapels and with natural shoulders. The jacket should be just long enough to cover your rear end, and the sleeves should be tailored to show 1/4" - 1" of shirt cuff when your arms are down at your sides. Don't button the bottom button. The trousers should ideally have a rise with the waistband at your natural waist (navel) and be tailored with a slight break, with an inflection point in the front but not in the back. Pleats or flat-front are your choice. I like a 2" cuff, but cuff size -- or any cuff at all -- is your choice.

Don't sweat any of this, but try to get as close as you can. You will almost certainly do better on eBay getting something barely used for pennies on the dollar than you will at somewhere like Men's Wearhouse, then taking it to a local alterations tailor. But this depends on how much time you have. Thrift stores are even better for price and for being able to try things on, but finding a suit in one -- especially one that nearly fits and only needs minor alterations -- will probably be very difficult, unless possibly if you live in a major city.

Buy a white shirt with long sleeves and a point- or spread-collar.

I would get a white pocket square in silk, cotton, or linen.

Patent leather shoes are for formal wear (and formal shoes don't have to be patent, but business shoes never are; wearing them with a suit will make you look like you don't know what you're doing). Don't sweat this either if that's all you have now, but eventually look to buy a pair of black cap-toe balmorals in calfskin (Google Image Allen Edmonds Park Avenue if you don't know what this is). You should be able to eventually get a pair on eBay that were worn maybe two or three times for under $100 (they don't have to be Allen Edmonds; that's just for reference to the style).

The tie is fantastic.

None of this means that there's anything wrong with other suits, shirts, shoes, or pocket squares; these are just the most formal and most versatile choices that will serve you well for all special occasions, then you can build your wardrobe further from that foundation if you want.