think of tomatoes as the ultimate test of truly learning gardening - to grow them well in many areas of the country takes daily monitoring for issues. But there are so many types that anyone can find varieties they can grow well. Small fruited ones - cherry up to golf ball sized- are quite fool-proof. The really large ones are pretty sensitive to differing weather conditions.
The really easy things - lettuce, radishes - are pretty quick spring or fall crops - great while you have them, but then the gap happens.
Swiss Chard - it stands up to summer well, is a great all purpose green, and is very easy to grow - and comes in great colors (Bright Lights variety).
Bush beans - lots of yield for the effort, can be canned.
Peppers, eggplants - easier to grow well than tomatoes, and if happy, can provide lots of volume, and can be easily preserved
Summer or winter squash are easy, but certain pests can really blunt the yields (esp squash vine borer).
Melons - yum! - but although easy to get going, fussy when it comes to weather - takes up lots of room.
Basil - easy to grow, yields heavily - and PESTO!
A few ideas for you!