I agree with Greg about doing what you can when you can at any point with the Roth. I say this even if you know you'll be over the salary limit to contribute eventually. I started my Roth in my 20s and some years could only manage a $1000 or so. I've only been able to max it out the last few years.
Also, I'm sure it's been mentioned but once you've got an account open, don't save up through the year and make lump sum deposits to it. Get the money into it ASAP even if it's $50 here or $100 there. If you're dealing with smaller amounts, especially if you're young and just starting out, you may find simply investing in a target retirement account is best. This way you can make the small deposits and not worry about having enough to buy a full share of a stock. You can't buy half a share of a stock but you can buy half a share of a mutual fund.
Here's a quick run down of the regular and Roth with minimums etc from Vanguard. I'd bet the other houses are similar
https://investor.vanguard.com/what-w...-and-roth-iras