I'll tell you what you can do to spend time in the game: Find new members for MAD! The big alliances have hundreds of members each. Some even number in the thousands. We need more people. Go out and find them.
As for tech trading, the basic concept is simple: Tech (like infra and land) costs more the more of it you have, so it's much cheaper for a young nation to buy (say) 10 units than it is for an old one to buy 10 units. So young nations buy tech and then sell it to old nations for more than the young nation paid, but less than the old nation would have to pay for that same amount. Both countries profit.
The game is extremely deep. There are a lot of little quirks like that you can exploit. There is much more to it than buying your 10 units of infra every day and then logging out.
If you want to know the basics for how to do well,
read this.