Proper running socks - try Stance f you think they's like gaudy. All the major brands are good.
Sleeves (tubes for the arms, enormously helpful in spring/autumn when you don't want to rug up completely but it's too cold to have bare arms from the off).
Books about running - try anything by Vassos Alexander
Voucher for an event entry (doesn't have to be a serious race - look for things like colour runs)
Entry into a mileage challenge, like a virtual LEJOG (finishers gear medal/T shirt). I've done there with a Company called End To End, others are available
Look on the RunThrough page, both for local race passes (might be over budget, but if you have a number of events near you it's the best VFM way to enter, and they can think of you year round. They also do kit these days, which is good, and last time I looked they had a very competitively priced massage gun
Or you could just be evil and get then a foam roller