I found 1st and 2nd on Civic were getting difficult to engage and the problem is when they get difficult to engage the natural reaction is to apply more force to gearstick, well I did the opposite and just use a couple of fingers on the stick - and guess what ? the gears engage a lot better..... talk about contra-intuitive.. problem is with more force you may be fighting the gate, and less force lets the gate guides the lever.
An oil change may help, but mileage for change is ( IIRC ) 70,000 for manual box, or maybe 70K or 7 years whichever comes sooner. An oil change is cheapest option as said by others.