I just want to ask what do you think I should buy now. I have all the teches L2.

It depends of how much food you have and how many people. If you are quiet with that (and if you are not playing in hard difficulty!), put every body on the research table and try to reach the level 3 of science. It takes a very long time (150 000 points!) but after you'll gain tech points faster. Don't forget to select one or two healer that you put on the research table, they'll work here, less than the others but they'll do it! And every time, watch their health. If they are tired, make them eating, or farming or make a stew (the one that restore them completely)

THANKS, I'll try to buy science

Your welcome!
Yesterday after I bought Level 3 of science, I was able to buy Level 3 of medicine (8 hours later! with 10 scientists, most of them are master) and one villager who was elderly became healthy again! You may try that!

My usual way is different to laurence's. I'll go first of all for farming, to make sure the villagers' supply of food is assured. I'll usually then go for medicine to make sure they will live and keep from being elderly as long as possible. I won't normally go for science until I've got the other techs (apart from exploration, perhaps).

It's what I have done with previous tribes.
In this tribe (playing in "easy" mode), I have food in abundance without coconuts or fish. But I often try to reach lev 3 of science the earliest as possible; it makes the other tech reachable faster!

Easy Mode

L2 medicine
L2 Science
L2 engineering
L2 Farming
L2 Culture
L2 Exploration

Medium Mode

L2 Science
L2 Medicine
L2 Farming
L2 Culture
L2 engineering
L2 Exploration

Hard Mode

L2 Science
L2 Farming
L2 Engineering
L2 Medicine
L2 Culture
L2 Exploration

My last is Exploration because its not very dependent and only some puzzles can do

Level 2 of exploration gives you the cauldron to make a stew. It could be helpful for restore your villager's health!

And it also lets you discover a piece of the gong!!

2 pieces of the gong!!! with the special stew!!