I can keep a "satisfactory" worker mix by keeping the ratios even, but I can't figure out how to get anything better. And advice?
Also, I'm not able to build an inner keep for my castle due to running out of resources. It won't let me order new pieces if the resources counter is at 0, which it always is by the time my outer-wall is constructed. I can't seem to keep resources on-hand no matter how many carters and quarry workers I employ. Anybody having more luck?

The number of resources is a cap on how big of a castle you can build. You need to build something smaller. As you go through the campaign it should let you build bigger and bigger ones.
As for worker ratios, the only way to get a perfect one is to have a perfectly even number of workers of each type and to have them work for a long time. They will gain experience as long as they are working for you, but if you don't feed them during the winter, that will force you to hire new guys which messes up your rating. On the bright side, once you do get them experienced, they build very very quickly.

Oh, I should also mention, don't hire unskilled labor if you can avoid it, they dilute the quality of your workforce, much like in real life.

This couldn't be more inaccurate. workers do not gain any 'experience'. Even numbers of every worker will always yield nothing higher than 'satisfactory'.

Good ratings result in certain mixes. The manual makes only a few hints by suggesting diggers are only need initially, and it's unwise to have too many unskilled workers as it can slow down production. Also it states masons are the backbone of construction..

these are just subtle hints though, you have to experiment to find proper ratios.

I haven't played the game in 15 years, but when I did I played it for six months solid because I had nothing better on PC. But I remember quite clearly stumbling around on workers trying to get the best rating for a very long time. What I remember is this: if you have any unskilled labour, you don't get a perfect rating. If you don't have diggers, you don't get a perfect rating, whether you are building a moat or not. I remember the manual led me quite astray on diggers. And lastly if you don't give them time, and you are constantly hiring and firing they never quite get to perfect. That's what I remember most.

Maybe the proportion of some types of workers is different, that I don't quite remember. I could have sworn it was even amounts, but I'm willing to back down on that.

I've just started playing this game a few days ago. Haven't been able to get past a "good" rating on the labor menu but what I did to get the "good" rating is to get like 20 diggers, 80 carpenters, 80 masons, 65 quarry workers, 65 carters, 30 smiths and 40 regular labourers. Those are the numbers I have after completing the first mission on a 3 castles campaign (duke difficulty btw).

From what I understand carpenters and masons are probably the main work force. Diggers are only needed at the start of every tiles' construction and maybe for moats (I'm not too sure about that because moats are listed under military and might be created by soldiers?). I don't think you really need more than 20 of those. Quarry workers and carters are probably related to the resources. If your resources are decreasing fast you need to allocate more men to those two professions. It's easier on the resources if you don't have your men working on too many tiles at once (even if you don't have the full complement for every tile).

I don't know much about how smiths affect your game/rating as 30 or even 20 looked fine to me up to this point. I guess you can completely avoid using regular labourers but by reducing them to 0 I couldn't improve my rating further and because they don't cost that much I just left a couple of them on the site.

I'll be trying more combinations in the future but I would gladly get some more hints how to actually get a reliable "excellent" rating.

Maybe it's an additional requirement of some sort of experience and also the wages you pay.