If you don't have time to build siege units to take out Kenilworth, that's fine-focus on baiting out blue's forces, since that's the time crunch.
To boost your gold output, grab the relics to the east-southeast fo your starting position (at the crossroads just beyond the bridge) and to the north-northeast (between yellow and green.) Remember you also have a market to trade surplus resources so you can have an uninterrupted line of villagers pouring out. Focus on getting up a castle early if you can for the Longbowmen. The baronial troops are roughly 40-strong by Simon, and he's backed up by the Kenilworth forces, which aren't much insofar as an army but whose castle you need to destroy is right by the camp. If you let your forces get killed and have to rebuild, this will take you much longer and be much harder than it really is. This isn't a problem as long as you follow the cardinal rule of this game, which you should know by heart-attack with overwhelming force. Your goal is to focus this enemy camp first, defeating his army before baronial reinforcements. A hero cavalry unit belonging to them, Simon the Younger, and a host of troops sit just outside Kenilworth. In addition to these troops are scattered blue Baronial forces. Around your base are three enemies you'll need to defeat (via destroying their castles and town centers): the yellow Welsh to the north green Kenilworth to the east, and orange Gloucester to the south. You now have a period to build up your economy and your army before your enemy realizes what's up. Note that your hero units only need to survive this phase once you reach the town they are valuable but disposable. Head to the inn, where your units will switch to mounted ones, and then ride east to the town if you're sneaky you can avoid some of the patrols along the way. Head up towards the highlighted tower there's just a few enemies to kill here, and then you can garrison in and out of it to get out of the town. You'll start off having to sneak out of an enemy base.