Good news for you - not much you need to spend money on before you start. Here's what you need
This usually varies by sector/region. I will say that you don't need to be fancy, but you need to be neat, especially at the entry level - meaning, you don't need to spend a lot, but those clothes need to be ironed, for example. For example, in the Middle East you need to wear suits (for guys, women wear abayas so they don't need to worry about anything in this respect), in the US most of the time you wear a shirt and pants. I'd have 1 suit ready regardless, and enough semi-formal/business casual clothes to last you comfortably for a week and where you won't need to wear the same thing every week. If you are a guy, have a few ties. I don't know enough about women's attire if you are asking about that, but follow the same/equivalent principles. That's the minimum. Some clients vary (US hospitals, investment banks, some government entities, some regions) - but wait until you are assigned a client and then just buy what you need before you start.
Get a decent roller bag - a lot of consultants get a Tumi brand. I survived for 2 years on a Samsonite $60 bag which no one complained about. You only need a larger suitcase for international trips - again, wait for the assignment abroad before you go spending.
My company provided one - send an email asking if this is the case for your company/office
None needed - all software will be on your laptop and provided.
What else comes in handy?
Being relaxed and ready to go!
For the most part, you should be able to survive at the beginning based on what you likely already have as an accomplished college graduate. If you are in a unique case you may have to pick up 1-2 extra suits or something, but wait until someone tells you something before you go spending.