There are ways to compensate for not having a protein skimmer, but they are a pain in the butt, and so you'll tend to not do them, which would hurt your water quality, and maybe your cephs. I'll explain the trade-offs as I see them:
A protein skimmer removes dissolved organic compounds (DOC) from the water before they have a chance to enter the nitrogen cycle and be broken down by denitrifying bacteria into, ultimately, nitrate. so, if you don't have a protein skimmer, the results will be:
1) Your colony of denitrifying bacteria will increase because of the abundance of "food", but only if you have enough live rock (or bio balls, or whatever) to provide space for them to live on. So you might need to buy more live rock than you wold otherwise need ($$)
2) Your denitrifying bacteria will produce more nitrate than they would if you had a skimmer removing their "food". You will need to do water changes more often than you otherwise would, to remove the nitrate. How much more often? Maybe as much as twice as often (SWAG). If you don't do more water changes, your animals will suffer.
3) All that extra bacterial activity will cause your PH to drop, so you'll need to add "Marine buffer" or something like that to compensate. Your PH will probably fluctuate more than it would otherwise, which might stress some animals if the swings are too wide.
You can limp along without a skimmer, doing frequent large water changes, while watching CraigsList or Ebay, looking for a deal on a used skimmer, which can easily be 50% to 80% cheaper than buying a new skimmer. Do your homework first so you know which ones are right for your system. I would look for one that is "rated" for a tank three times as large as the one I have. Most manufacturers exaggerate their ratings, and octopus tanks produce more waste than reef tanks of the same size.