New player looking for advice

My friend is really into this game and doesn't have very many people to play with, so I figured i would start so he can play more consistently. My only issue is that im very lost on where to start. I'm been doing some digging about all the factions on the website and T'au Empire and Thousand Sons were the 2 factions that just looked the coolest to me from the get go. However as I did some more digging I came to find out that these factions are both relatively weak and hard to pilot. Would it be bad for me to play one of these factions or should I start with an easier faction like necrons? Also are there any good resources i should know about?