PPC Keyword Strategy

Either is fine depending on your goal, but the main thing you have to be aware of is creating conflicting groups or campaigns. This is especially true for broad match modifiers. If you split some good keywords off into their own ad groups (which is smart) then you have to make sure they aren't still fighting the original ad group during the auction. You control this with ad group level negative keywords. Use the Ad Preview Tool to make sure the correct ad group is now being triggered.

If you decide to refine the keywords within the original ad group - based on the data received - then you have to make sure the more refined keywords outbid the less refined. For example:

+buy +widget (Bid: $0.50)

You get traffic that says a lot of conversions are coming from buy blue widget, buy cheap blue widget, where do I buy a blue widget. You can add a new keyword to that ad group as...

+buy +blue +widget (Bid $1.00).

If blue widgets and green widgets are doing well you can create an ad group for blue widgets, and another for green widgets.

In your original ad group you would then add a negative keyword for blue and green to keep those keywords out.

If you find out that blue widgets are absolutely smashing it and you want the budget to be massive - just for the blue widgets - then separate that off into its own campaign and have blue as a negative keyword for the original campaign.

One more advantage of going Fraggler's suggested way is, you can change the wording of ads as well so it will increase the quality score because of keyword relevancy with ad text.

Firstly find the related keywords
then define the bids
and start running your campaign
hopefully you will get better results with related keywords.

A drop off in traffic isn't necessarily bad so you need to ask yourself, why? Firstly, by the sounds of things your original campaign may not have been setup properly so you could have been getting bad traffic: have conversions dropped off?

If it is a drop off of good traffic then find out which search terms are no longer sending traffic and you just have to debug your negatives. Adwords has a dimensions report (or search terms under the keyword tab, or under analytics too) which says the actual search terms sent you traffic. Go back to when you were getting decent traffic and look at this report; now go to the period after the changes are see what's changed.

It's just a case of debugging and it is very easy to lose a lot of traffic after a campaign is cleaned up as you're no longer paying for dud searches. The Ad Preview tool can help find errors but running through searches yourself with pen, paper, and a flow chart of your campaign structure is better. You might have a negative add wrong or at a campaign level instead of the ad group level.

Find what traffic you lost and debug.

Keyword Strategies are essential to developing winning search engine marketing campaigns. ... When visitors click on your ads in the Search Engine Results Page (SERP), you pay the amount that you've bid on the keyword. This process is known as pay-per-click (PPC) advertising.

Certainly the long tail. You can build the same amount of traffic from thousands of long-tail terms father than
you can through one or two head-terms.
keywords are more specific and targeted. Although the search volume is way too few from broad one, they are
easier to rank and get high results in SERP