First off, endgame items are much, much harder than early game items. For example, for the same amount of money you can get a Bulwark of Ages or a Mageslayer and an Orb of defiance (and having 16k to burn is ABSURDLY rare unless the game is evenly matched), and both of those are totally different and valid (though orb of defiance probably isn't the best investment, you get my point).
Early game, it's generally Scaled armor+Scalemail/potion/scaled helm, or the lowest level of priest minions. Midgame, you want to get your one mana helm and stack health and maybe gloves with proc effects (and a wand of speed). But it all depends on the build.
