play garen top, play yi jungle, play katarina or annie mid, play ashe adc, and play leona support (all suggestions dont listen to this too hard haha)
yi is not a good jungle to start with since he can be counter-jungled easily and has to get really fed to be anything above worthless
hecarim, zac, rek'sai and vi are all easy junglers that still contribute to their team even when they're behind
kat's also a character that takes a lot more effort to play correctly than just pressing a couple buttons, talon is probably the easiest assassin for mid lane
i'd say these some of the easiest and least situational characters to play:
tops are garen, maokai, poppy, darius, sion, whatever i'm really skewed on easy to play top lane because i understand how to use most top lane characters
jgs are the four i already mentioned
mids are annie, veigar, ahri, anivia and viktor
adcs are tristana, jinx, sivir and mf
supports are sion again, soraka, lulu, janna, sona, really most supports are super easy to play because they're meant to not take mechanical skill but rather have to manage a bunch of item actives
none of those characters are really difficult to just pick up and know what abilities to use, what to max, what to buy, how to play them correctly, etc