For the start, i will pick up some mid grade ewaste. Not low or high yielding. Low yielding waste could have very high processing/shipping cost for you in the small scale - could become frustrating from the beginning of the venture. High grade could be tough to access for good price, because of well established business around it. But if you have opportunity to get it for good price, then why not. If the price is low in your country, there is high probability that selling processed waste, eg IC chips, gold plated items, pins etc. would be tough in your homeland due to established business in this field.
First thing i would look up is, if it is possible to ship concentrated values to countries where the buyers can pay better money. Restrictions, bureaucracy, paperwork, permissions, limitations, taxes, tolls... etc. Calculate if it is worth all the trouble, fees and time. Also dont forget the import laws of the country where you will be shipping your product. It could be considered a waste material, and many countries have tight regulations on waste import.
Also, you need to know what you are dealing with. If purchasing bulk, not processed waste like whole computers, telecom stuff etc. you need to know whats inside. If purchasing boards, you need to know how to evaluate the value of each individual component - for precious metals and base metals included. You need to be prepared for quick assaying of the sample of material to asses its value for further negotiation with seller.
When shipping, you need to reduce the weight of the material to minimum, thus lowering the shipping cost. Consider making some sort of concentrate, which should be homogenous = easy to sample and assay. This is key for successful deal with your customer = you know what
you have and what its worth, your customer recieve exactly what you promised = happy customer, returning to make another deal (especially when you are shipping abroad and can´t make deal in person).
Purer product you make, more it could be considered a "precious metal" by authorities. This could be troublesome in some cases, as export and import laws could force you to pay more taxes and fees.
Many of this you probably already considered, but that is what I see as a must for starting more on the successful side
I wish you good luck