I wanted to unlock this very early in the game so did the following:
I started the game with the
Triumph Street Triple and didn't spend any money upgrading it.
This bike gives you access to the following group of events in World Tour Mode
Naked Bikes: Under 700ccI was able to get gold on all 5 events.
The Time Attack event may be tricky for some, you can get it at this point though as I managed it and unlocked
The Against the clock achievement in RIDE worth 29 pointsWin a gold medal in a Time Attack event of the World TourI was only able to Gold medal the first 3 race events with the stock bike
In the races the AI, even on Very Easy will pull away from you on the straights, but you should be better under braking and able to catch up and pull out a lead over the 1st & 2nd place AI to secure the wins.
Skip the Drag Race and Track Day events until you have an upgraded bike as you will be un-competitive with the stock bike
World Naked Bikes: Middleweight GroupI was able to Gold on the first 2 events, which then gave me enough credits to unlock the achievement. You may need to do some additional events in this series.
The single race was straight forward and for team race I chose Luka Schulz, who finished high enough with my win to also get me the following achievement.
The Tag Team achievement in RIDE worth 33 pointsWin a gold medal in a Team Race event of the World TourThis took around 90 mins, give or take 15 minutes either side as I did stop to write a couple of solutions along the way.
The other option for getting this is to buy lower priced bikes to open up the other group events and win races in those series to get you to the 100k, but I was specifically going for this achievement without doing that.