Some phrases and words that can help you to connect ideas and make your essay more organic -

To add and ideas use the following phrases -
Furthermore
Moreover
Correspondingly
Similarly
Whereas
As well as
Along with/coupled with 
In addition to
For instance
As an example
A case in point
A telling example

To show cause
Accordingly
Consequenty
Because
As a result/consequence 
For this reason/purpose
Therefore
Thereupon

To show contrast
Comparatively
Different from
Even though
Although
Conversely
Instead
In comparison
Whereas
On the other hand/contrary
Besides
Otherwise

To add emphasis
Above all
Certainly
Assuredly
Particularly
Unquestionably