TheMangelo, welcome to Stryleforum.
Congratulations on your up and coming graduation. Whereever you work, as the new grad, you are going to be required do site work for sure whether you want to or not. Most companies will do this to you to give you experience, which you will benefit from anyway. You have one suit at present, so you are ok for now. You probably won't need it very much. Better invest in:
- 2 pair safety rated steel-toed shoes or boots with rubber or nylon soles.
- hard shell down-filled jacket
- hard shell down-filled vest.
- several pair of chinos.
- several work shirts and undershirts
- a few pairs of decent work gloves
- a utility belt to carry tape measures and gear.
- a decent ruck sack (nap sack), also to hold gear or a change of clothes
Once you start, talk with and get to know the senior engineers. Ask a million questions and they will be happy to teach you. They'll give you the best advice as to what will serve you the best within the firm. Marks Work Warehouse and Eddie Bauer are going to be essentials because you will certainly get dirty doing field work. No need to invest in nicer clothes yet. At interview, ask if work clothes are a requirement and if the company can get you a discount on such things. Some do and others do not.
Don't toss your streetwear just yet. You'll find that you are still going to be wearing a lot of it.
What you can do is to purchase a sport coat or two, one in tweed. These are powerful accessories to your wardrobe and can be dressed up or down, yes even with denim. Wishing you success in your career.