You can expense things for tax purposes regardless of whether you incorporate or not, if they are legitimate business expenses. It goes on your Schedule C either way.
You can be a sole proprietorship instantly on saying "I'm a sole proprietorship." The first form you'd file would be Schedule C the following year. Colorado or your municipality may require a business license and/or a DBA ("doing business as") filing. My business was just myself DBA my trading names for ~6 years, until I started to get clients with employees who had titles like Senior Counsel for Vendor Contracts or Compliance Officer. At that point, having the 2 LLCs just made it much easier for them to do business with me.
You can get your LLC in Colorado if you find that to be convenient. Nevada is also quite popular -- they issue them readily online, maintenance is a breeze, they have no state income tax (you'll pay Colorado's either way but there is zero risk Nevada will attempt to get frisky with you, which is a risk with extraterratorial registrations), and their fees are fairly low. ($325 per year or so IIRC.)
The reason to segregate bank accounts is twofold:
a) (The big one) Having separate accounts makes it much, much easier to retain accurate records on income and expenses, so you pay only the taxes you legitimately owe rather than donating extra money to the USFG because e.g. you forgot a few hundred bucks of SaaS subscriptions on your personal AMEX.
b) (Far smaller) Keeping things firewalled between your personal finances and the business makes it harder to pierce the corporate veil if your LLC ever gets into legal trouble.
You should certainly open a new credit card and use it, and only it, for any business expense. It does not have to be a "business" credit card or issued in the name of your company. You're going to just take the statements from that and hand them to your bookkeeper, saving you hours of pain come tax time.
tell me if there are other perks.
There exists a spectrum of aggressiveness in the small business community on how much they take advantage of this, but: what you think as a natural human is clearly a business expense, what the IRS will invariably sustain as a business expense, and the maximum you could possibly claim as a business expense all have huge swathes in between them.
This is probably only worth a few hundred bucks a year for you, but, for example, your WSJ subscription will invariably be held by the IRS to be a legitimate business expense, on the behalf of any business whatsoever. This essentially means you get to buy it with pre-tax dollars, which is an effective X0% discount.
There are things that are a bit more aggressive. Ask your accountant where the line is. (After you have $10k in revenue, find an accountant.) This is what they're for.