From an environmental and cost standpoint, you can't get much better that gravel. It's permeable so there's no surface water runoff, and the carbon content of the paving materials is much less than with products involving polymer resins or asphalt. In fact a large part of the environmental impact of gravels and other aggregates is associated with transporting them around the country, so try to choose something quarried locally if possible - no Cotswold limestone if you live in Aberdeen! Whatever is sold most cheaply in local builders' merchants might well be a good starting point.
If you want the gravel to stay put, more angular pieces of rock will be better than rounded river gravel ('pea gravel') which is great for drainage but can't be compacted to form a secure surface covering. My neighbour's drive is rounded gravel and is forever migrating onto the road outside, whereas mine is more angular and there isn't an issue. Another way to help retain gravel is to have a raised edging, e.g., of brick, with a humped strip of stone or block paving at the gateway as in the pic posted by @ApolloandDaphne above.
Ideally choose harder materials like granite, flint or harder limestones rather than softer stuff like sandstone or the popular Cotswold buff limestone which will crush to dust under the wheels of your car over time.
Gravel also has the advantage of being easy to repair invisibly if work is needed on pipes buried underneath.
A good gravel driveway will need a decent compacted crushed stone base, I've seen 100mm quoted as suitable but this would be a bare minimum. I'd specify 150-200mm, and hope that gave reasonable certainty that a suitable depth would be achieved in practice, rather than specifying 100mm and ending up with 60-80mm in places....
There's more info here: Gravel, Cinder and Hoggin Paths and Drives | Pavingexpert
And an outline written spec (which you could use as a starting point for getting prices, even if you plan to get a proper spec drawn up by a landscape architect or similar) here: Typical Specifications | Pavingexpert