When I dig my trench for the main power feed, I'll lay a second conduit that for the time being will be empty. If I ever need it, it'll be there. If I never use it, conduit is cheap so no big loss.
Internet I'm hoping to run through a wireless repeater. 2.4G is pretty crowded in my neighborhood, but 5.8G seems to be far and few between for the time being. With 100MB/s coming into my house I' guess I'll see how fast I can get anything in the garage.
Without a repeater both my phone and laptop are fine on the side of the garage closest to the house, but the other end, 50' further away seems to be a different story. the fact that the router lives behind the TV in the living room doesn't help, as the living room is on the opposite side of the house the garage is on.
For me, a powerline adapter may or may not work. I have two services coming into my house from when it had been made into a duplex back in 1970. It has since then been "unmade", but I still have two functional meters on the side of my house. One of them will be going through a main shutoff in my basement, then straight to the garage, running the entire house of the other one. Two services, two meters, two main feeds, but coming off the same transformer.
So plan A is a repeater, plan B is to use the conduit for a Cat6 connection between the routers.
As for the OP, I would bury an extra run of conduit. But not spend $$$ on wire until a repeater has been tried.
Both Walmart (15 days) and Staples (14 days) have a satisfaction guarantee. 2 weeks should be plenty to find out if a repeater will work for you or not.
edit to add Best Buy does as well, 15 days.