I find Exploration a decent thing to do when playing Advent and I control a good number of worlds. Advent's Divination ability (fairly low level, Civic/Harmony ability) allows them to explore at more reasonable costs, for a fairly steep initial price, that is.
To fully explore a world, you need to sink 1,000 credits, 325 metal, and 200 crystal into the project. Fully researching Divination (two steps) costs 1,700 credits, 225 metal, and 275 crystal, so not cheap at all. But it cuts the cost of exploration in half. With Divination fully researched, fully exploring a planet costs just 500 credits, 163 metal, and 101 crystal.
Total savings is 500 credits, 162 metal, and 99 crystal (it's supposed to cut it in half, but some odd numbers mess things up) per planet. Divination effectively pays for itself after exploring three worlds (after just two for it's metal cost) and after that it's a very nice thing to have if you're into exploring.
I've been waiting until later in a game until this kind of project is feasible and then going for Divination then spamming exploration on planets. The sad thing is though it usually yields just a lot of "Our scryers revealed nothing" over and over. Even with a lot of territory, I often don't find many bonuses that ultimately justify the costs of exploring in the first place. A couple of the income bonuses are nice, as is the artifact that allows for increased damage, but it's all very expensive and risky.