Yup. Zinnias. The easiest of all annuals to grow yourself. That said, some of us are better than others at actually remembering to sow those succession plantings, and it might make sense to just order what you need when you need it.
Benary Giants are huge and productive and colorful. The industry standard.
Oklahoma have petite flowers that are welcomed in bridal work when the Benary's are too big.
$.175- .189 per plug grown in a 216 cell tray, billed as 210