Love this game. but i was wondering which system is good to be. I mean Hi tech. like in old elite there were few main systems. in this game.... too many systems. where to go?
Gaining reputation with the three main factions tends to take a very long time, so in the beginning it's better to focus on gaining reputation with subfactions that are loyal to the main faction you want to support. Eventually, once you've become Friendly and/or Allied with a number of subfactions, your main faction reputation will shift to Friendly.
You gain reputation with subfactions by completing missions from them on the bulletin board, by purchasing and selling commodities at stations they control, by turning in bounties and exploration data at stations they control, etc.
The faction menu on the right-hand UI displays the subfactions relevant to the system you're in, and which main faction they're loyal to. When you've done something which increases reputation with them, a small blue arrow will appear next to their name.
I wouldn't look for good systems so much as good areas. Pick a patch of space with a good mix of systems and economy types, ideally high population ones, and if some of those systems are owned by a faction that you want to gain rep with then so much the better.