Buying gold you get 2 week ban if caught but a bulk purchase may be risky, I recommend buying it in segments to keep yourself safer, I know multiple trades may sound risky but believe me it's a lot safer as it's set of alarm bells if you purchase 1b straight.
I got banned on my maxed main staker and I barely did actual rwt on it. It got banned while I was holding 300m for a MM trade and didn't get a 2 week ban either. So it can happen but it's not as common as it used to be I think.
This was probably like 2ish months ago. The traders involved were searchy (reputable) and someone else who was a little established so a chinese IP could be a possibility.
I would say if it's longer than a week from your initial trade you should be fine. Usually the only bans I have heard of are trading over weekend, ban happen early the week after when jagex are back at work I imagine they would take action as soon as they are aware so they can get the gold out the game also This is different to what happens with botting, as they do delay bans to monitor the behaviour of the bots and also so boys aren't always aware of what action got them banned
On this topic, what would be the best way to trade/transfer multiple 100m's from account to account when buying to avoid being banned? Just trade in small increments? Stake it?
I've rwted tons with tons of sketchy trades over the past years and only got banned once for RWT. This was when i picked up some gold on a fresh lvl 3 i got banned few seconds after i took it. Honestly if u use a VPN and a mule with a decent level to pick up the gold u should be good.