Well, that's a great start! Two lenses, 18-55 and 75-300, give a lot of range of focal lengths. As for accessories...a decent flash unit is nice for indoor work, and for lighting up many types of scenes both in the sunshine AND in the near-darkness. A decent, yet reasonably priced tripod is nice. A tripod can be a mixed blessing--a pain to carry at times, yes, but it can also be a huge asset. A tripod allows you to shoot slow-speed shots, timed exposures at night, and also can help you set up the camera, meter, and compose, and then take a photo, and review on the LCD screen, and make minor adjustments, to refine a composition.
In one way, a tripod is a BIG learning tool. It allows the user to do the timed exposures at night that are so fun, and allows you to shoot sharp, steady shots in marginal lighting conditions, like window-light still lifes, which are otherwise very difficult to do. I would look at the $100-$130 tripods on special from
Adorama on-line, for example, as a place to start.