Since you are considering using these activities, I will assume you have a decent amount of red dice (3/4) and a decent denier engine that allows you to support them. Here's my two cents:
At 4 pips per activation, Chivalry is an expensive Activity card to use, especially since you have to use your remaining red dice to determine the amount of cubes you can place in the Event cards. And since most Event cards require at least three cubes to defeat, using them as a VP engine may not be your best choice; it may be more cost-effective to counter the Event cards directly.
Having said so, using Chivalry can set you up to score a bunch of VPs on a future turn, since you can place these cubes on different Event cards, and get the majority/ preferential spot on more than one (whereas attacking them directly limits you to placing all your cubes on the same card).
Joust, at 3 pips, is more likely to be useful, and it guarantees you are getting the VPs you want. There's only six red dice on the board, so as long as you have a decent red roll (or spend Influence points to re-roll/flip) you are likely to have the red pip majority on your section of the board.
You should always buy a red die from another player for 2 deniers so you can use your total red pip count to activate Joust (and if you buy it from a player who has red pip majority, it puts you back on top). Hopefully you can do this several times in a row (once no one else has red dice, you can start using your own red dice to activate the card; you'll still have majority!).
As always, the Activity cards combination will greatly affect the strategy you have to follow in order to win the game. Without knowing what other Activity cards are revealed, it's hard to say this plan will work for you 100% of the time.
For example, if the Blacksmith Activity card is in play (which adds 5 pips to your red dice selection), then you are pretty much guaranteed to have the greatest amount of red pips on the table, so you should definitely follow this plan (as long as you are the one who activates it!). However, if that one isn't in play and there's no easy way to get Influence points, you probably won't want to spend them to re-roll your red dice, and you will be stuck with whatever roll you get, which may diminish the effectiveness of this strategy.