Would you make a purchase from several suppliers and go through a logistical nightmare, or pay extra money and buy everything from one supplier?

The answer is  Total cost of ownership .

I would meet with the supplier that has a stable stock count with decent quality and negotiate a further discounted price by laying a offer on the table to have all our business but with2 conditions in mind:

1.) Discounted price across the board of items (even if its2-5%) because of the larger business volume the supplier will be getting from the company.

2.) Guaranteed availability via contractual basis to protect your stock readiness.

If those2 conditions cannot be met for some reason then i would choose to have at least3 suppliers available at all times.

Actually, this depends on the type of the materials you are purchasing and related suppliers availability.

But as a general practice , you have to study "well" and compare the advantages and disadvantages of each way in order to have a clear idea about the best way you should follow.

"You should never put your eggs in one basket".. it preferable that you have many validated suppliers to diverse your bass in order not have shortage if the one supplier fails...in today's world of technology there is nothing called a nightmare... so it is better to have many channels of supply violable as you can compare prices and quality ...

purchase goods from one supplier after a negotiable agreement of delivering the goods on time.

It's always good to have 2-3 suppliers in list and having a chance to compare among them. It's pretty good to have a plan B even in this field always. 

It is simple to say that to make sure the availability of the items/goods from the supplier before making the Purchase Order (PO) to avoid any trouble in the end.

It depends, if i have a luxury of time in the project schedule, at that time may i take the decision to purchase the required material from several suppliers in order to achieve a money saving or on the other hand may i proceed with one supplier if i have a tight project schedule.

it depends upon the availability of goods , sometimes we have to pay minor difference to fulfill the needs 

that is totally wrong logistics is not a nightmare 1st  lesson in supply chain that purchasing is a  process in logistics even if you will go through one supplies  2nd even if you will depend on one supplier you should also apply logistical way starting from your purchase order till it reach its final destination

*can i ask what if you depend on that one supplier and at the time of delivery he had a problem how you will solve it sure u will use your logistical way to help you  

* what if he lost you shipment or he was late how you can control that ?

if you have a a logistical knowledge it will help you will use them to solve that problem 

purchasing is a part of logistics 

Depends of the type of materials you purchase