Alright early summer is the GREATEST TIME of the year for South Europe.
Especially when u r a fan of nightclubs lol
Then my advice would be:
Enter Europe by Portugal and all the way north.
Portugal is worth at least a week (for me). Lisbon & all those sightseeing spots around (like Sintra, Estoril & Cabo da Roca) will cost u at least 3 days, and then u might wanna spend a couple of days in Porto to taste the nice wine and chill a bit.
Then to Spain, man there's so many cities u should visit. But with that little time u have, I suggest a quick tour in the South of Spain which will take u more or less 5 days (of the city I can come up with right now, Sevilla, Cordoba, Granada, Cadiz, Ronda, Marbella, etc., u have to make your own cut
). Then all the way to Madrid and its surrounding cities, which will take u about 5 days as well (some must-visit cities like Toledo & Segovia, and Aranjuez would be nice around the time u're there as well, these cities are GREAT for a one-day trip cuz they're close to Madrid), 2 days are enough for Madrid itself (but I think u really need to dip into it to experience that city, won't have enough time though). Then from Madrid to Barcelona & Valencia, that would take u a week, I personally LOVE Valencia, its food & drink (oh u really need to taste the paella and the HORCHATA there). Then from Barcelona/Valencia u can go to France.
Paris itself will take u at least 3 days, and then u can visit Nice/Cannes/Monaco (they're in the same area), and then maybe u wanna see those lavender in the province of Provence, u might go to Marseilles for a couple of days, but remember, book the tour EARLY.
For me Spain has the world's greatest discos (actually all South Europe has AMAZING nightlife), so enjoy yourself there.