If you're not into tailoring as a hobby then you can get a lot of clothing for cheap as you wont care about smaller details that will run up the cost of clothing. However, if that is the case then you want to prioritise comfort, and the slim fit stuff you see around will be unconfortable unless you genuinely are very slim, and at that point slim fit should still drape and not be clinging to your body.

There is so much advice to give on this topic that it requires some reflection to think about what questions you want answers to. Keep in mind that its a bad idea to buy a full wardrobe in one go because you will change in what you like wearing, so buying slow to make sure you buy things you are happy wearing is important. You want to feel confident through your clothes at work because you're there for so many hours per week!

Theres a saying, for buying nenswear, that you can only pick 2 out of 3: quick, quality, and cost. Cheap and fast will sacrifice quality, quick and high wuality will be expensive etc.

I would advise against the shirt and trouser look without a jacket personally. A navy suit is an easy answer to your problem tbh. Consider oxford shirta if you can get aeay with it bc they go with a suit and tie equally as much as jeans and trainers. Speaking of shoes get dark shoes, not tan. Get 2 pairs of shoes to rotate them as they'll need a days rest between wears to last you longer than 6 months