Very little unless it's a proper return to sump setup. Money would be better spent on baffling the sump.
Are you using much oil?
Unless you're running boost, there will be very little reason to add one. Catch cans basically catch blowback through the head from pressure. With boosted setups they are quite an essential part, but with a standard power N/A setup, they're not very much use. Save your money bud