I send a standard of 15k cav to every Valley I ever attack and come back victorious every time, w/ losses anywhere between 100 and 3k, dependin' on number of pikes. I don't bother scoutin', but if I did I could send layers to soften the losses against enemy pikes.
Upgrade your Academy until you can start to lvl it up. You'll require a Stable (which requires a lv5 farm) to be in the same city you're researchin' it as, and it must be of equal lvl or higher than the research you want to begin.
i.e, you must have lv5+ stable to research lv5 HBR.
Very low lvl Valleys...lvls 1~3 will produce Crosses. Medals don't drop too often, especially if you're on server 10+ so jus' keep at it.
Sayin' that, the free gift package for beginners (the gift box icon in the top left corner) should give you all the Cross medals you should ever need, iirc.

