Building Tank is fine. You can still carry in low elo through a tank role, but if you find a carry role easier then that’s fine too ( this is personal ).
Farming against poke ( Syndra/zoe) is annoying but
never use normal autos, and don’t be afraid to fall behind on CS. Usually you can use an empowered AA to kill the melees ( assuming they are low) , and use your Q to do the same on the casters. After level two most of those matchups get easier since you have W. If your oponent is hyper aggressive (standing in front to negate XP) you can use your q to farm both melee and casters seperatly but might lose some CS wich is fine. You strengths outweigh theirs in map pressure.
When the lanes break down , always force your Bot to mid and take over their lane. Bot lane farm is now safer since it will be pushing towards you (probably) and it gives you a more comfortable Ult mid lane in case of a fight.Most bot lanes do this naturally but if they don’t then stay on their nerves about it cause it’s largely beneficial for both sides ( they take towers faster, you don’t share XP etc)
Lastly, roaming is galios middle name. You can effectively do this as early as your first back, or , if you are less confident , as soon as you buy protobelt. This lets you shove lane faster than most champs hence giving you lane pressure. At level 6 you should always let your JG know that they can be more aggressive, so they Can Invade , do herald etc because this forces a safe lane to either stop playing safe ( Wich means you can gank it) or if not , you can just Ult your jungler when he’s doing his risky buisness. So I guess the short answer is , very often. ( just as a side note , even you leaving lane at level 6 is still good map pressure without even having to gank, since the opposing mid lane will probably spam missing pings ,forcing all other lanes to play safe , letting you or the JG place vision or do dragon/Herald)