If you have a good lvl 1 CC (like a thresh, or blitz) you should consider invading. If you have multiple (like a midlane lux or top lane nautilus), you should definitely invade.
Unless you're a high enough elo (and if you're asking this question, you're probably not), then you can probably assume the opposing team has no clue how to effectively counter an invade. So long as your team remains grouped, doing a fast, early invade will likely have one of the following outcomes.
- Best Case: You get a pick and kill them. (Even better, they burn at least one summoner and you still get them).
- Commonly: You get a pick and they burn a summoner to survive.
- Worst Case: You get engaged on and have to burn a summoner.
It's not likely the enemy is grouped enough to burst someone down on your side. Even if you get caught, it'll most likely be by a group of 3 at most, which most level 1's can survive so long as long as you don't Leroy Jenkins it. If you invade early enough, you can hopefully blow some of their summoners, recall, and will likely have enough time to get back and leash with full hp without missing any creeps.
Additionally, you may end up starting a level 1 fight, in which case it's best to remember to not get too greedy, else you overstay and lose the advantage due to a long recall and lost creeps.
Just remember to be mindful of timers, to get the advantage while you can, and to take advantage of whatever you get out of the invade. It doesn't matter if you burn the ADC's flash in an invade if you don't take that 5 minute window to harass, zone, and hopefully kill them.