So you're kind of asking for a tanky melee fighter with a gap closer who is easy to play. Ones I can think of:
Never played him before, but he doesn't need much gold to be effective. Somewhat of a teamfight oriented champ, but since your playing bots, he should be good enough. He's got a gap closer that you can combo with your slows to get in range for.
He's more of a jungler, to be fair. I'm assuming from what's your asking you want toplaners? He kind of works toplaner. Again, since it's bots, it doesn't really matter. His hook is a huge gapcloser, plus it stuns. If you toss at terrain you can drag yourself forward. You've got lots of CC, a huge %HP shield.
Extremely strong. She's more of a hybrid tanky assassin with a gapcloser and a conditional stun. She's not the easiest to play, but very snowbally, a lot of kill potential, a strong top pick, and a huge power spike once you get that
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I've never played him before, but he has plenty of gapclosers, a relatively common "noob" pick, I think.
Super tanky. His ult is really his only gap closer. But he's pretty easy to play, plus he has a pretty hard slow.
I would say, basic noob champ. Q is a speed up + silence. W is an armor buff. E is he spinny move and his ult is a high damage execute. Passive keeps you healthy out of combat.
Other champs that don't fit your criteria but are relatively easy to play (against bots):

I would recommend you try Annie so you can practice placement (she is so immobile) and also keeping track of stacks of your passive. If you do end up trying Riven, be forewarned that she is not the easiest champ to master. If you end up playing PvP as her, you'll run into a lot of issues. (I would personally recommend Cho'gath because of his innate tankiness with his ult and the fact that he is one of the only champs left who has an AoE silence. However he's very immobile.)