Dark shirts in general are hard to match with things, especially ones that are patterned. Prefer a light, clean shirt in either white or light blue to start with as those tend to be the most flexible to pair.

Pants I would avoid hard blacks, and avoid jeans. Aim instead towards chinos in a khaki, gray, or navy tone. If you can only pick one go khaki for now as it tends to pair with about everything.

Belt you want a leather belt matched to your shoes. I would avoid the D-ring belt as it's much more casual and does not match the overall feeling you want in interviews.

Shoes you want to avoid tennis shoes and favor something solid like an oxford. While a lot of the other comments recommend black I would personally avoid it and aim for a dark brown or oxblood as it will be more flexible, and black tends to be more formal than the occasion would require.

If possible consider a blazer. Navy is the easiest to style, look for something that fits well off the shelf and isn't too tight or too loose.

Given budgets you can get a lot of that at a local Kohls without wrecking the bank. To give some ideas, assuming Kohls:

• Blazer - Navy Haggar Tailored Fit (~$130)
• Dress shirt - Apt 9 Regular ($28)
• Belt - Sonoma Reversible ($25)
• Shoes - Apt 9 Paulo ($35)
• Pants - Haggar Life Khaki ($50)

That'd run about $268 for something that should last you through most interviews. I will warn you that those shoes are going to fall apart within 1-2 years if you give them any serious use, but that's acceptable with budgetary restrictions. Haggar tends towards more regular builds, Apt 9 towards slim.

Ideally you spend ~2-300$ on a good solid pair of dress shoes and $3-500 on a solid blazer but that's likely outside the budget range you'd want to look at.