How big is too big?

How big is too big?

So, I am building a raised bed this spring. My plan is to rent a rototiller, till up the soil under it and top it with purchased topsoil and some leaves to the depth of about 8-12 inches. I'm planning on making one large bed, in an octagon shape (16ft on two sides, 7 ft on four sides, and 8 ft on two sides) which should put me at around 350 square feet. It'll be a mix of annual herbs, veggies, some marigolds, nasturtiums, zinnias and whatever others strike my fancy. Maybe a trellis for beans in the middle, maybe not. And maybe some rosemary bushes so it isn't barren in winter (though does rosemary not play well with others? hmm... must research). And a couple of paths through it. I've done some gardening, but my biggest bed was about 7 by 10, so not nearly as big. When I look at the space, I'm not too daunted, but when I count the square feet and think, I could plant 300 tomato plants! I'm daunted. I sort of figure though, I'd rather just put in the big bed and be done with it rather than add on annually or something... Am I being over ambitious?
New kitchen for me

New kitchen for me

Wine bottle lamps

Wine bottle lamps

Purple Tree

Purple Tree

dormant or dead?

dormant or dead?

Photos from this week’s adventures in gardening

Photos from this week’s adventures in gardening

Plant id

Plant id