jt,

Why dont you build a frame out of 2 X 4's or 2 X 2's?

Remember that it makes your life easier if the gutters have less slope when the plants are small and young and then increase the slope as the plants get bigger. You can just put more wood under the high end as the plants grow.

The absolute lowest cost way to get a hydroponics support bench is to visit garage sales. Look around for end tables or furniture or whatever works.

The only problem with this is that your wife may not let a $5 piece of furniture anywhere in the house.

You can also support the gutters on a cinder block with a brick or wood pieces on one end & just a cinder block on the other.
You are using shorter lengths of guttering, but if you have a long piece of gutter with heavy plants & a media, the guttering can pop out of the brackets. If you want to hang the gutter you can use the gutter brackets &/or reinforce it to a structure by inserting rust proof screws through the gutter. At certain points on the upper part of the gutter, there should be holes in the side, which screws can be placed through. Another option is making a hole at a stable place in the upper guttering with a soldering iron & then inserting a screw into your support structure.
I have also built a frame, as DRKboss suggested. It depends on what you want to do.

I think the frame DRK was talking about would work best. The problem is that I don't have any experience in that. Is there some website that shows step-by-step information on similar projects?

Get four of these sawhorse brackets and some 2 x 4. Build two horses, lay your gully across them and you are done.

Sorry picture got deleted by mistake.