For real, free gravel for life is the choice. You can start a gravel business and sell that shit. According to Google a 100ft driveway can cost upwards of $3k to gravel.
The real question is, does free gravel mean you can spawn gravel? Or buy it for free? Both require a good amount of logistical planning to take advantage of to build a gravel empire
The logistics isn't that much of a problem. Start small and make yourself a name by being trustworthy and way cheaper than the competition. If you succeed at this stage you can hire people and expand in no time.