That is going to depend on what powder you use. With Ball powders  (#9, 4100) i strive for 10 FPS.

40 Rod

Hard question to answer at times when it is low groups can be quite large. And at other times when it is quite high groups can be quite small. I have learned to just ignore it and to go with what my groups are telling me and to not let it crawl into my head. Or to let it try and dictate to me what it is I am trying to accomplish. That is trying to get all ten of my bullets into the same hole at 200 yards. I also feel the same about velocity it is what it is when all is said and done. That is when I will actually check it for future use or just wanting to know. It does come in handy when trying different powders and such as the bullet typically does like to be in a certain velocity range. 
JWL 300MP is also what I use.

Just to be cheeky, the lower the standard deviation the better. 

There will not be an ideal range for a loads SD as it will change with powder, cases, primers etc.etc, When I was shooting and competing nationally in benchrest comps I always worked loads until they shot horizontal strings then got down to trying to read the wind. Looking through an old note book I managed to find a combination that had a 3fps standard deviation. 

And for those that maybe remotely interested all my modern bench guns have Hall actions. Sure wished I bought a single shot when Allen made them.

My best plain base loads with fixed ammunition run single digits SD over my Oehler 35p.

JWL,
What caliber/cartridge are you loading?  Black? Smokeless? Duplex? 
This may be more info than you are asking for but here's sharing some of my discoveries...
I've attached some data from a cartridge I experimented with  diligently recently.  I've learned a few things - velocity and accuracy can really vary depending on caliber.  The data with the 44 shown, as velocity increased all my numbers got worse, and so did accuracy.   I have a couple cartridges I'm working on right now.  One such is a 50-90, as the velocity goes up my numbers are changing slightly but accuracy is getting better.  The problem I'm having though is felt recoil is becoming intolerable - for me...   
I did quite a bit of experimenting with this 44 cartridge in a high wall and shot it for one season.  As I went up in velocity the ES and SD escalated and accuracy went down the tubes.  The data shown here had this rifle shooting fairly consistent MOA groups to 400 yards.  Beyond this the accuracy fell off and frustration escalated - just personal though.  I spent a lot of energy trying to make black work in it and to some extent it did but not so much with grease groove bullets, it likes PP, dual diameter, but the operator didn't care that much for it.  The SD with all the other propellants was usually in the mid teens.

I don't have real good data to share on the 50, but in my notes pushing the 785 gr at 1000 fps, the SD was  low and group size was 2-3 MOA.  When I had the same bullet going 1400+ the SD was in the low teens and if I focused my groups were hovering around 1 MOA.  This is my caliber choice for the season so I'll have more later...  Can't say as though I'll take the abuse to stay at the better accuracy so it may be a marginal season - but - I'm trying to make this a mile gun so to keep my sight staff height reasonable, I need the velocity, thus recoil...
My nickle's worth.
Regards,
Greg