Sounds like the clutch is not releasing properly... could be hydraulic, could be your clutch cover is knackered (happened to me like this few months ago) could be one of the cylinders is knackered, release fork is bent/collapsed, release bearing is shot, could just be low in fluid, could have air in the system...
Under the gear lever gaiter there are two springs one either side of the housing if these aren't set up something like or if they're worn, then it can be difficult to engage gears.
Bleed the hydraulics first. Top the master cylider full to the brim, and creep under to open the bleed nipple on the Slave cylinder. Don't pump the pedal. Just watch the flow and spot any spurts or bubbles. It should bleed clean through just this way.