Those renders use the full morph sets and high quality skin textures and probably "skin shaders".

Definately you need skin texture... I don't know what is free but maybe you could look at http://www.sharecg.com/b/11/poser? for maybe a character with free texture. People like BaginsBill's VSS but I don't understand it... There are "shader" products by face_off and 3Dream that apply fancy shaders to any texture and they do good results... I have used face_off's Real Skin Shader with plane "bucket fill" textures and had them look good. face_off has a tutorial on how to build the shaders without purchasing his products... it worked for me when I started but then I bought his product for convenience.

You need to morph the face too... there are free character heads at that freebie site above and at http://www.most-digital-creations.com/ if you don't want to or can't afford the full DAZ morph set... those characters can be blended to make new ones. If you have no budget you should find a "Poser Magnet" tutorial... I recommend one by Traveler, Dr. Geep, or PhilC. Magnets can reshape a face or other body part to create original morphs. Also most-digital has both magnet sets and original non-DAZ morph sets.

For a free male figure fully loaded with morphs find byAnton's Apollo Maximus. Maybe someone can recommend a good free female with morphs. In freestuff here dphoadly has Posette-V3 which has many morphs but requires the P4 Nude Woman from the Poser Legacy content. That takes Victoria 3 textures of which many free skins are around.  Also there are Nea and Zenon Poser 4 figures by pitklad  which are free and take Victoria 2 textures and Micheal 2 textures of which some free are around. http://www.renderosity.com/homepage.php?userid=63835

The Poser 5 and Poser 6 Poser 7 and Poser 8  built in figures have morphs and can be played with in Face Room to create new skins and characters (as can Apollo).

If you have $29 DAZ used to have a great 3D Content Starter Pack that had Reduced Resolution Micheal 3 and Victoria 3 with all their morphs along with texture hair, clothes, animals a dragon and a nice forest setting. There is still a lot of free stuff for those characters around. I like Reduced Resolution Victoria 3 even for male characters.

There are some "how to start" tutorials at DAZ under support that suggest how to make renders without purchasing additional content.