I'd not be in a major rush to wean from 4 months tbh. If your baby is doing well on milk then maybe go a bit longer. If he is sleeping well and not waking at night often seeming hungry I'd be inclined to wait a while. But thats just me.
Anyways in answer to your questions
1-what's the best high chair? and is the bumbo thing the small ground chair better to start with? which brand?
Your LO needs to be able to sit up unaided for a high chair to be of use. So don't use one to start with if you do wean from 4 months onwards. Bumbo's are good and you can get them with a tray so can put food in front of LO and he can try things himself as time goes on.
2-what type of blender do u use for ur babies food?
Just a simple hand blender. Steam all the veggies and the fruit that needs it and then mix in a little of the water and blend to a mush.
3-what did u start weaning him on? juices? food?
Not juice at all. Don't go there till at least 6 months. Just water is fine for now. In fact don't give juice at all is my way to go. What LO does not have he won't miss. Bad for teeth when they start coming through.
You need to start on simple foods and flavours. Here is a site with info, scroll down and read the weaning part and it tells you good foods to start with.
http://www.eatwell.gov.uk/agesandstages/baby/weaning/
Don't give foods containing milk, gluten, nuts and a whole other list of things till 6 months plus (and in some cases older still). Stick with fruit and veg to start for the first few months. Then past 6 months you can introduce meat and pasta etc.
No salt. No added sugar.
4-what is the best baby recepie book ?
Annabel Karmel does a good starter one. 100 purees or something its called.
I think you really need to read up on things for yourself so you are aware of the guidelines on what foods to avoid and what to try to include etc. And from what ages. For example don't give honey to a baby under one at all.
BBC website also has some clear and useful info
http://www.bbc.co.uk/parenting/your_kid ... ning.shtml