Root Domain/Blog Domain/Wiki Domain

Hello everybody,

i want to to seo on my site as well as on blog domain but little confused about this situation,can someone help me here?

i want to improve ranking for my domain site-dot-com for keyword (a,b,c,d,e)

i also want to improve ranking for my blog domain i.e blog-site-dot-com for keyword (p,q,r,x,y,z)

now here site is one but 1 is main domain and second is subdomain so is there anything where i can be penalized by google or can i do seo for both domain with different-different keywords?

why so different?

if keywords are in the same topic i'd go for a subfolder. otherwise if very different use a subdomain. regardless of how it is you won't get penalized.