For easy, in the heat of August, definitely sunflowers and zinnias. The Sunrich series sunflowers has a "lemon" with dark center that is really a nice clear yellow if that is what is needed. Don't forget to succession plant to make sure you have them when you need them. ; ) They take about 65 days from seed.

I would also suggest dahlias, celosia and gomphrena. By the way Lisianthus is one of the most difficult cut flowers to start from seed. I've done it a few times and it's always a challenge. They need 5 months to bloom from seed so you would need to start them right now in a greenhouse. They grow very, very slowly at first so it takes a lot of patience and close attention for the first 2 months.

Strawflowers..Gotta have those!

fillers Add to your big blooms:

Ammi- (white/greenish) for filler
bupleurum/baby's breath- for airy filler
eucalyptus- greenery

give the bouquets volume, character, and interests