The City of Serres is a lively city that you can visit on a budget.

You may find the accommodation of your taste and budget in relevant sites, e.g. Booking, TrivagoTripadvisor.
Keep in mind that some Hotels are in the suburbs of the City and you may need a car or taxi. Most sites in the City as well as the IHU Campus are in walking distance form the center.

There are also many interesting and picturesque sites to visit nearby, e.g. the Cave of Alistrati, the Kerkini Lake, Fort Roupel, the Monastery of Timios Prodromos (John the Baptist), etc. See some suggestions in Tripadvisor, DiscoverGreece  and

When in Serres don’t miss the opportunity to dine, drink, and feast. Don’t forget to try Bougatsa and Souvlaki, the latter with a glass of local wine or ouzo.