Hello.

I am starting out on an installation job, and I want to know if I should be leaving small expansion cracks between each board? I don't want the wood to expand and bow or cup. Any thoughts? I also have a room that is long way's paralell to the floor joists. Does anyone see an issue installing parallell to the floor joists if the subfloor is 3/4 plywood.

Solid hardwood? Ideally wood should be acclimated to the annual average moisture content for your location.

Flooring has been acclimating for 2 weeks.

Get a moisture meter and check the MC of the wood. It'll acclimate based on its mc and the relative of the area where the wood is. Length of time does not guarantee correct mc.

If you cannot get the wood to the right moisture content to match you average moisture content for your area, you can provide an expansion gap between rows as you lay the flooring. It will take some figuring and a moisture meter.
Harbor freight has an inexpensive moisture meter that you can use to find the moisture content now and with the principal that your specie will expand a little with each percent of moisture content that it will become when the climate changes you can leave the appropriate gap. Usually the gap is not between each board, but every five or eight rows, whatever you calculate to equal to a spacer that will take up the space to provide the space for the wood to swell when the climate has changed. There are expansion coefficients for each specie that tell how much a 2 1/4 inch wood strip will expand with each change in moisture content percentage as determined by engineers.
Sometimes we spray the flooring with a garden sprayer to help shorten the time it takes to acclimate, saturating the surface so the wood can absorb moisture that can spread throughout the whole board over time.

I got a meter but it only goes as low as 7%. Both hardwood and subfloor did not register. Assuming it's got some moisture even as low as 3% that puts me in the range to not be worried correct. No need for expansion gaps? I was considering putting tiny washers as spacers every 4 th or 5th row.
I'm going out to get a better meter that starts at zero. And assuming they are within range am I ok to leave no gap.
Also I was reading about starting in the middle of the room and using a spline to change the direction of the board so expansion is more even. Is this worth the effort?

Where are you located? Wood species? Board width(s)? The rule of thumb is to start in the middle if the room is over 20 feet wide. You can do it even if the room is smaller. Starting in the middle means that you may have to adjust/mill the last row on two sides of the room instead of just one side. Not a huge amount of work to do it. You'll most likely be using splines at some point e.g. going into a closet, so this would give you some practice early in the project.

Is it possible to have a zero MC of the wood.

I just tried out my second Moisture meter which has a range of 0-35% for hardwood. I am still getting nothing. I've tested virtually every surface in my house and the only one that I get a reading on is my granite counter at around 13% (set to Masonry). I've tried a pin and pinless meter. the floor that is here does not seem to undergo much movement. There are a few small cracks here and there but nothing major.

I live in Southern Ontario (Canada) so Cold dry winters, hot humid summers. Is there a less gadget dependant way to figure this out. The largest span i'm doing is 14 ft wide. I'm pretty much ready to put a washer row every 8th row and call it a day. Not sure what else to do.

Any further help would be greatly appreciated.

One last point. I have an air exchanger that I set to 50%

Is 50% the relative humidity inside your house? Are the meters calibrated for your flooring species? The mc of the flooring coming out of the mill could be pretty low. What kind of reading did you get on the framing lumber in your house? Subfloor mc? Did you buy from a local mill? If so, you might want to give them a call and pose the question to them.