In volume ratios I have always found 1:2:3 in ratios of cement:sand:aggregate to work well for foundations paths and drives. Just scale up to the volume you require.
The mix for a footpath to the backdoor, the foundation for an house extension or a driveway to the garage can all be done with a 1:2:3 ratio if you're mixing it yourself, but better results will be obtained with readymix. Readymix is superior to the stuff you mix yourself but works out dearer. You will be asked what the concrete is for and the mix will be adjusted according to your requirements.
Bear in mind that you need reasonably close access for a mixer truck and if you are doing a large project you will need some assistance to work the concrete or else it will partially set before you can get to it. A retardent will only work for so long.
Yes, the dry mix is good for general work, and works out cheaper because you won't have a heap of gravel/sand and a 3/4 bag of cement left.
If you need the work to be visually pleasing you can add a couple of drops of dishwashing liquid in the mixture, this will retard the setting of the cement somewhat so you can play around longer when you are floating the top off.