Is it just me, or do people find putting together a plot deck of 7 much harder than a card-deck of 60+?

What do people think is the most important factor in building a plot deck? do you start with the stats, and worry about the special text later Is the text more important, and there's a way around the stats?

I've had problems in the past putting in plenty of claim 2, and getting low income. This weekend I played Kingsmoot, and really suffered from a lack of initiative.

What would be the top tips for putting together a good plot deck?

There is never a specific answer to this, because it's all about the synergies between your draw deck and the plot deck, and plots that are amazing with one deck can be terrible with another.

Really you can actually deck build either way...

1. Many people can actually build their entire deck around their plots rather than the other way round - for example, Holy deck with Power of Faith x2 and Powers Long Asleep. Maester/Shadows decks with City plots. Greyjoy Valar based super save.

2. Build your deck, then look for the plots that fit your deck best. Or maybe just your playstyle. Build a Stark Seige deck - play as many extra mil challenges plots as you can and then add a couple 2 claim and a couple high initiative ones. Bara rush - Almost all high initiative plots maybe.

Some plots are just often good in general. It's almost always good to have at least one high gold plot - Song of Summer, Muster the Realm, and the Fury plots are always good (unless you want a different restricted card than the Fury), Retaliation is almost always a great card. One reset to hold in reserve if needed is almost required, decide which works best with your deck and in your meta then add Wildfire or Valar. But really, it's all about synergizing your plots with your deck, and every deck's is just a bit different.

Getting your plot deck right really is tough especially when you are building your plots deck to your main deck.

If you need to go first most of the time then you will need to aim for mostly decent initiative on your plots, if you wish to play last or your deck doesn't care too much what order it plays then you can mostly not worry about this. That said you probably still want at least one that has a good chance of getting you initiative for those times when it will matter.

If you can play your deck cheap then you wont have to worry about your gold numbers as much and you can include more of the weaker gold plots for there other effects.

A reset of some kind should almost certainly be one of your plots for when things don't go as planned.

Once I have narrowed down my options based on gold and initiative values and have chosen my reset then I usually try to add at least one claim two plot, and one high initiative plot if I haven't chosen plots for initiative and then I go for effects. The plot effects can make a really big difference when they play well with your deck. I usually come away with about 10 or 11 plots for my plot deck and then pick the 7 that seem most likely to work and play test to see what needs altering.

If you aren't building your plot deck based on the rest of your deck (like Freerider mentioned, Holy decks use 1-2x Power of Faith, Siege needs multiple M challenges, etc) then you can build it based on your needs. There are some plots that are almost auto-include if you don't have a reason to not include them. Retaliation! (4 gold, 2 claim), Valar (or some other reset), Fury (just for the stats if you dont have another restricted card), Respect of the Old Gods (again, basically 4 gold, 2 claim), Rise of the Kraken and To the Spears fit in most decks when the House is appropriate, Loyalty Money Can Buy is always good, etc.
As others have stated, after any auto-includes, build based on your gold/initiative/claim needs... i.e. if you can get away with low income, feel free to load up on 2-claim plots(my Gen Con GJ Choke deck ran five 2-claim plots and never ever had a problem with income), if you don't need to worry about initiative (and many decks don't) don't even bother looking at initiative stats. If you are building the rest of your plot deck after you have already picked a few for the effects, fill in the missing gaps with high-gold and high-claim plots.
Except for a few notable exceptions (City plots will almost always start with At the Gates or City of Lies) the most important thing might be to make sure the plots can be played in whatever order is useful - don't build a deck that requires you to play the plots in a certain order unless the deck is really really consistent.