This achievement is only as hard as you make it, it may take a few attempts but follow some basic rules and you will fly through it. Moderate AI will stop trading with you once you take a large lead, so set yourself up for some easy victory points early on and you won't notice the lack of trading.

Development cards will be your greatest ally, so you may choose starting settlements that will give you lots of wool, grain and ore. You can use Soldier cards to steal resources from other players, or Road Building to grab the two VP for the longest road.

Be sure to keep an eye on how many settlements you have as there is a limit to how many you can keep at any one time, upgrade good positions into cities (also gaining VP) so you don't trade all of your resources to build a settlement only to find you can't build any more.