It depends what kind of high you want, sativa or indica or what?
If I were ordering from Peak today I would be getting their Skunkberry, just came back in stock. I have their Northernberry on the way I'm told and it's supposed to be a very potent strain.
Right now at Seedbay you can get annaC's yummyD(Yumbolt x Alpha Diesel) or Triesel(Strawberry Diesel x NYCD x Alpha Diesel). annaC breeds exclusively to provide excellent seeds for people in need of good strong strains at a low price. Seedbay charges $5 shipping per strain but if you could come up with another $10 those are KILLER strains for $25 each including shipping. Problem with Triesel though is it's a 75-85 day strain. But those two strains give you world class genetics, one strain for day, one probably a little more suited for night time when you're not that interested in going out and doing things. Seedbay is pretty easy to use also, just register like you did for this site, log in, go to the "auction" and buy them, fill out your order form and print it or include the exact info from the order form with your "auction" number and mail it off. I sent by regular mail Monday the 12th and it was mailed back to me Monday the 19th. I should have it in around 16 calender days from US to Great Britain and back. Either of those strains at $25 each with shipping is a deal.
If I'm not supposed to mention other outlets on this board my apologies.