The best way to get fast wild windsown weeds, for finding wheat seeds out of that, is just train your exploring level to 16-20.
At 20, you see every wild windsown seed there can be found, at 16 there are some you cannot see.
So, when you have 20, you just explore (hunt, map some places, get leeches, steal, find mines...) until you find wild windsown weeds.
Normally, you don't really have to look after for them, they will sometimes just be on your way.
Then, when you have the weed, you must dry them on a herbelist table. After a while, there will be a seed in your table, you just have to be lucky then for finding wheat seeds out of it.
Me myself, I found my first wheat seed yesterday! (at 16 exploration level). I found the seed after 12 windsown weeds, I think I was pretty lucky accually. My brother though was very lucky in finding that seed, he also got it on level 16, but he got it with his 1st wild windsown seed!!! OMG!!
Other seeds to find: carrot (to train perception), pumpkin (for a nice halloween hat, and for food), onions (food I guess

), grapes (needed for making wine!), hemp (for plant fibres), flax (also for plant fibres), poppy (a red flower, decoration), hops (for beer), tea (for making tea, duh!, very handy for your stamina!!!).
NOTE: wheat is the most rare seed!! Sorry if there are more seeds, I did not mentioned...
Succes in finding your own seeds!!