Because you are new to this, I would have to say start small and work up in steady, small steps. You can burn a lot of money in no time if you are not carefull in maintaining visibility. Also, be sure to use conversion tracking (AW or your own) where applicable to help find what yields the highest ROI.
I began with mainly low ticket items, whilst taking a few opportunistic pot-shots at some high ticket things. I don't think I really had the click volume at that time to do the high tickets justice - £1 a day just isn't going to get you many loans sold. But you never know when you might strike it lucky on the google roulette wheel.
Right now, 10 months down the line I'm very firmly on low/medium ticket stuff, on mostly 'nickel' clicks, which seems to be what's working best for me. I have a high ticket campaign which is making good returns, but I'm still not happy going above £0.15 per click on it. Raising your CPC too high is where you can really lose it.