In DotA, people stayed in base until creeps spawned to avoid this kind of thing; unless you wanted to have ward play, in which people traveled as a team to place ward(s) "safely". All in all, don't go out of base until minions spawn, unless you have wards to place, in which you should travel as a team.
I simply act as a living ward for my team's jungler *in all matches*, since I usually play mid.
If at least two people have teleport on our team, we'll have three people try and gank the enemy jungler at 1:55 at the golem, then teleport to their respective lanes, since by then their team should start appearing in the lanes (if they remain MIA at 1:55, the plan is scrapped).
If the enemy team has heavy teleport presence, we'll usually simply stay behind our towers until their entire team has appeared on the lanes to make sure they aren't gonna 5-man gank us.
Edit: Also note that this isn't a game that can be applied in terms of pure logic, since it's based on player skill and individual unit strengths/abilities as well. A well-picked 3-man team could easily beat a worse-off 4 man team, for example. As such, it is impossible to generate a generalized best strategy as you described and one must instead formula strategies on a case-by-case basis instead.
If at least two people have teleport on our team, we'll have three people try and gank the enemy jungler at 1:55 at the golem, then teleport to their respective lanes, since by then their team should start appearing in the lanes (if they remain MIA at 1:55, the plan is scrapped).
If the enemy team has heavy teleport presence, we'll usually simply stay behind our towers until their entire team has appeared on the lanes to make sure they aren't gonna 5-man gank us.
Edit: Also note that this isn't a game that can be applied in terms of pure logic, since it's based on player skill and individual unit strengths/abilities as well. A well-picked 3-man team could easily beat a worse-off 4 man team, for example. As such, it is impossible to generate a generalized best strategy as you described and one must instead formula strategies on a case-by-case basis instead.

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I am an Ashe player.
When I was still new to League of Legends—say from level five to fifteen—I used to think I was a bit of a badass. At the start of the game of just about all of my games, pairs of two of my teammates would go along the side paths, while I would take mid. Usually, this consisted of me running all the way out to just beyond the range of the opposing outer turret, looking to take some early potshots at some unsuspecting enemy champion. Occasionally, I would get a couple of hits in. Most of the time, however, my lane opponent would stand just out of my reach, protected by the turret. My summoner level and ELO rating eventually increased, though this had little to do with my whimsical early game plan.
Then it happened. One day, the opposing team utterly demolished me.
The game started like all of the rest. My teammates went to the top and bottom, while I took mid and ran straight up the middle. I found another Ashe just inside my reach, and I fired a couple of shots her way. She retreated back toward her turret, and I chased her down looking to get in one more arrow.
That’s when her entire team came rumbling out of the bushes. It was 5 vs. 1. I need not tell you that a character as squishy as Ashe does not last very long in that type of battle.
After the game, I began thinking more about my strategy, the opponent’s gank, and why I find so few other players willing to meet me half way for an early exchange of fire. It didn’t take me long to realize that I was looking at a “safety in numbers” type of game:
I want to avoid as much game theory jargon as possible, but basically this game is telling us that you should not want to engage unless your whole team is there.
Think of it this way. Due to the fog of war, you only know what your team is doing in the first ninety seconds; what your opponents are doing is their private information. Suppose I am all alone in the middle. The other team does not know this. Does it make much sense for me to engage the enemy?
Well, not really. In the best case scenario, my opponent is also alone and we exchange some shots or I find no one else at all. But if my opponent is willing to engage, I have to wonder kind of information that is conveying to me. He does not know how many people I have in the bushes waiting to gank (zero). He does know the number he has waiting, which I am still clueless about. Thus, if my opponent is willing to start the battle early, it is a good signal that there might be a gank going on. As such, I should retreat back to my turret and wait until minions spawn until advancing forward again.
We can extend this logic further. If both sides are willing to engage in what appears to be a two vs. two battle early on, then you should probably retreat…unless you have a third waiting in the bushes. But if the other side is still willing to engage, they might have a third and a fourth lurking somewhere as well. That means you would only want to continue if you had your entire team there.
The bottom line: rational players will only want to take on an early battle if everyone is there for support. Wait until minions spawn or other opposing champions make themselves visible on the map before going any further. Don’t be the fool who goes and gets himself ganked early on looking for a minimal reward.