What color are the glads and the daylilies? Any chance you can post a picture? That would help a lot.

I wouldn't recommend planting in rows, but the glads will get taller then the daylilies (at the least the foliage, the flwoer spikes might get as tall). So I would put the glads behind the daylilies. I have never planted liatris but when I googled the shape looks similar to the daylily, so I would put them maybe in the same grouping as the daylilies, not necessarily in front or behind them, but mroe "with them".
I don't like seeing individual plants, so I plant things close together and I dont really garden symetrically. If you like the symetrical look then lay it out as such.

I fee llike you need a different-leafed plant in the mix. The leaves of all three of these plants seem to be grass-like. I would add either a geranium (spring blooming) or chrysanthmum (fall blooming). Yarrow would also look nice, but it also grows about the same height (maybe slightly smaller), but the fern-y foliage would look good. It would also bloom about the same time (all summer). Another addition that would look nice would be catmint (nepeta). It's a lighter, more open and the flwoers are a pretty purple.

In the fall you might want to add some spring blooming bulbs to have some early color :)

I hope that helps a bit. good luck!

Thanks for the advice. I re-posted this message in the gallery section and included a picture of the corner I was focusing on. (link below) The gladiolus are pink and the day lilies are yellow. When you say you plant things close together, not symetrically, could you give me an example?

Here is a link that might be useful: same post, with picture

Daylilies grow all different heights: for instance, the common Stella De Oro is said to be 11" (oddly, I have one clump that height but another clump much taller), while Hyperion is 36" and some spiders can be 6'. If you know the names of your cultivars, you can look them up in these databases:
http://db.tinkersgardens.com/
http://www.daylilies.org/DaylilyDB/

A general truth about grouping plants -- not only daylilies -- is that they usually look better in odd numbers. I like to plant daylilies in a triangle -- three small clumps about a foot apart. That way, they have more presence, but aren't so crowded that I have to divide them all the time (though in my limited experience, different cultivars spread -- grow new fans -- at very different rates).

I've never grown glads; the ones we had in my childhood were quite tall, so I'd put those against the deck, and probably in a row so they don't hide each other. If you don't have info about the height of the ones you bought, you might ask on the Bulbs forum if there's a good database for gladiolus varieties.

Pink Event is a tall glad - count on the flower spike being maybe 4' above where the bloom stalk breaks out from the leaves. They also tend to open facing the sun.

Nothing looks more pitiful than glads planted too far apart or lined up in a row, like soldiers marching off somewhere... And glad flower stalks are heavy, they'll likely flop over on you once two or three of the florets open. Be prepared to stake them up if you go for far apart and in a row.

As an alternative and to help with flopping - plant glads a bit deeper (at least 6") and closer together than is generally recommended on the packaging. If I had 18 glads, I'd plant six corms an inch apart in three six inch deep holes. No matter the depth or closeness, it takes 80-90 days from planting to bloom.

And, glads are inexpensive (as in cheap) - they're showing up now in every color of the rainbow at Menards, Home Depot, Lowes. Get the ones labeled "Grandifloras" if you like big florets on tall spikes. You can see in the box that the corms are good sized, aren't dinged up or moldy. Many of them will already have a sprouted tip - that's a good thing.

I don't grow glads all the time - when I do, it's not for color in the garden, but rather for cutting and use in indoor arrangements. They're magnificent when they first start opening - once the florets start climbing up the stalk, not so much. The foliage stays green and upright all season so hiding it isn't much of an issue.