To be an isolationist means you will not expand your empire past your home planet.  Instead, you will focus on building up your home planet as much as possible.  As an Isolationist, you cannot be attacked. Scows can still dump waste on you, but since your happiness cannot go negative, this just means you would get more resources, since waste is a resource. This affords you the benefit of not needing to worry about buildings that others will need to expand and instead focus on maximizing your production and exploration capabilities.

Recommened settings for Species Affinities:

Species
The isolationist can start out as any race, including human, but there are some advantages to creating a custom species.  The following explains the pros and cons of putting points into various affinities.

Habitable Orbits:  3 or 5
Since you won’t be expanding past your first planet, it doesn’t make sense to put extra points into this affinity.  Instead, choose either orbit 3 or 5,  both of which can build second tier food sources (Dairy Farm in orbit 3 or Beeldeban Herders in orbit 5).  These will help to limit the number of food plots needed to get a decent amount of food production.

  Orbit 5 may even be the better choice as you'll be able to get access to 4 different food producing glyph buildings as orbit 3 only has access to two.

Manufacturing: 4+
This stat will help you build things faster.  You don’t need to have it at a 7 but since it will help you deal with waste and build ships faster, you shouldn’t go below 4.

Deception: 1
As an isolationist, you won’t be spying on anyone.  Don’t waste any points here

Research: 4+
This affinity reduces the cost of buildings.  While this may not be extremely important, there is no reason to take the below a 4.

Management: 5+
With only one planet, you are going to want your buildings to complete as fast as possible.  Don’t take this below a 5 and consider taking it all the way to 7.  This stat also is very helpful at later stages of the game as it also decreases your ship building time.

Farming:  4+
Resources are the name of the game as an isolationist.  Don’t take this below a 4

Mining: 4+
Again, you can never produce too many resources as an isolationist.  Keep this at a 4 or higher.

Science: 4+
The more energy you produce the better.  Keep this at a 4 or higher.

Environmental: 4 or less
Waste is only helpful to isolationists if you wish to recycle it for additional resources.  For this reason you shouldn't take this higher than a 4.

Political: 1
Since you aren’t going to be expanding, your happiness can never go negative, therefore this stat is worthless to you.  Do not put any points here.

Trade: 5+
As an Isolationist you are going to be doing a fair amount of trading.  Consider taking this affinity all the way to 7.

Growth: 1+
There isn’t really a good reason to put any points into growth as an isolationist.  You will very quickly be able to increase your PCC.

Essentia
Isolationists do not require as much essentia as other types of empires.  Expect to need a minimum of 100 essentia to start in order to afford a few weeks of boosts, but after that you will only need limited amounts in order to recycle and perhaps facilitate trades.

Infrastructure
Isolationists have the luxury of being able to take their time to build.  You are not under any stress to get to your second planet.  Perhaps the only thing you may need to worry about is getting your university high enough quickly so you don’t have to travel a long way to mine asteroids.

Start out by following the tutorial to completion.  Once completed, feel free to demolish the intelligence ministry since you won’t be needing it.  Keep your University within one or two levels your other buildings.  Don’t bother to build a capital or stockpile until your University is level 14.  After that you will need it if you want to continue to grow.

Waste
As soon as possible, built 1 waste sequestration buildings and 1 recycling centers.  These will allow you to store and use the waste you produce to build faster.  As soon as you are able, start recycling your waste.  You don't need to worry about happiness as an isolationist so waste is only useful to you as a means to gain additional resources.

Resources
Food:  You need to produce 4 food types in order to ensure that you don’t lose happiness when you build.  Orbits 3 and 5 planets will allow you to build at least 4 different food types.  Build four different food types (don’t bother building malcud fungus farms if you don’t have to).  Once you have a level 5 corn plantation or denton root patch, demolish your lowest food producing resource (other than the denton root patch) and put up 3 dairy farms or Beeldeban Herders.  These will be your main source of food.

Water:  Water is one of the most difficult resources to produce.  Build 4-5 water purification plants and keep them as close to max as possible.  Once you get to level 7 or 8, start replacing them with water production plants.  You won’t need more than 3 water production plants at higher levels

Mines:  Mines produce a bit more than water and food so you don’t need as many of these.  Start with 3-4 mines and replace all but one of them with mining platforms later in the game.

Energy:  Geo energy plants produce enough energy for the early levels.  Build 2-3 of them and replace them later with either Fusion Reactors, or if you can hold out, Singularity Energy Plants.

Storage:  It is important to have enough storage to build the higher tier resource buildings.  Have at least 2 and possibly 3 of each storage facility

Other Infrastructure
University:  Make sure you can support your next level of university before upgrading.  The University sucks away more resources than any other building so rule of thumb is to only upgrade once all of your storage is maxed and your resource buildings are maxed or close to maxed

Development Ministry:  You’ll need this building in order to increase your queue.  Build one and get it to 6 or 7.  Any higher is a waste.

Network 19:  Not necessary, but may be nice to know what is going on in your area.

Space Port:  Build this up to 5 or 6 early so you can start probing.  You want to find good asteroids to mine in your area.  It also helps to know your neighbors.  You may decide to build a few of these later on to support lots of ships.

Shipyard:  Build to level 3 or 4 initially so you can queue a few ships at a time.  Start looking for asteroids and exploring as soon as possible.

Observatory:  You will need this to build probes.  Build to 5 or 6 in order to be able to probe the stars in your general area.  Eventually you will want this maxed out.

Trade Ministry:  Keep your trade ministry maxed out so your cargo ships can carry the most possible goods.

Archaeology Ministry:  Keep this as close to max as possible.  Glyphs buildings are going to benefit your colony since they don’t take up extra plots.  You’ll want as many of these as possible.

Notes:

1)  Make sure you start exploring as soon as possible.  You’ll want to find as many plans as possible.

2)  Isolationists are very welcome in alliances.  They are very valuable when it comes to space stations because they do not have to be defended.  Find a good, active, alliance that will allow you to participate in end game activities.

3) There are 4 ways to lose your Isolationist status (the game client will warn you before you do it).