The synchronizers may be a tad worn. You might also change the manual transmission fluid as well. Make sure you use what the manufacturer specifies and make sure it is compatible with your transmission. Certain gear oils can be damaging to your transmission.
Some manuals require a synchromesh fluid, some take a standard motor oil, and some even take automatic transmission fluid. Read the manual.
If it hasn’t been changed in a long time or since the car was new, you may find the fluid has broken down and been contaminated with wear metals and quite nasty. If so, refill with the cheapest 5W30 or 10W30 you can find and drive the car with this for a day. Then drain that out and put the proper fluid in. You may have a magnetic drain plug and see lots of metal stuck to it. This is not a big deal as long as you don’t see big solid pieces.
This makes sense with it harder to get into gear in the lower gears. They are more straight cut so weak synchros will show up more in those gears. This is typical. Everything you mention makes me think the synchros may be the culprit. You let the clutch out which gets everything spinning at the same speed, then it goes into gear easier when you put it into gear.
I would change the fluid before rebuilding. I have seen it improve things but don’t expect perfection.