I would calculate the monthly expenses that are eligible to be paid by credit card, and get a card with no more than double that limit (account for larger expense months). So if your cc-eligible expenses are $1000/month, get a card with a limit of $2000.
I use my cards for everything, (I have 11), like using them as a loan (0% promotional rates), and change the card I use based on the type of purchase and what gets me the maximum cash back. For example, I have a card that earns me the most cash back for gas, another for restaurants, another for travel, another for grocery...etc.
I have even used my cards for free "cash advances"; I'll sign up for a balance transfer promo, and if I don't have anything to transfer I will still transfer a couple thousand from the card I use the most (general purpose), so that it goes into a negative balance. So if I am at negative $2000, that means I can spend on the card without having to pay anything up front, until I spend the negative balance of $2000. Then the only thing I have to worry about is paying the minimum on the card I transferred the balance to, and make sure I pay it off before it's due (typically 12-18 months).
Obviously I don't think this is the correct current course of action you should take, but I wanted to show the opportunities that abound in the magical world of credit cards. Credit cards can give you a lot of control over your finances and can earn you points, but also save you interest since you can take advantage of the many 0% promo offers out there, vs getting a loan or borrowing from your 401k (which astounds me how alot of the same people who have chided me on my cc habits, have paid way more in interest and fees for borrowing money, than me. Ex. I currently have $40-50k in cc debt...paying not a cent of interest. I renovated my fixer upper $40k worth...paid no interest).
CC get a bad rap, and fortunately with new laws it is harder (but not impossible) for cc companies to be tricksters. So you still need to educate yourself. If you have a sturdy efund, then by all means play around with paying expenses off with a credit card, or even borrow so that you can save your cash earning interest in your savings account.
The best single piece of advice I can give you, and which I still remind my self, is to never spend credit AND cash (except for expenses that can only be paid with cash). That's when it seems people get off the rail. They are only using their card for "emergencies" or for "gas". That shit's too confusing IMO. If you're going to use your credit card for expenses, use it for ALL expenses, and then keep ALL of your net income in cash accounts, ONLY taking cash out for cash-only expenses, and to pay off your monthly credit card bill.