Gill Sans alternatives
There’s really no need to use Gill Sans anymore. Even if you think you have to, you may get away with one of these alternatives. My favourite is Dover Sans by Robin Mientjes
Other humanist sans-serifs in a similar vein:
Agenda, Greg Thompson, Font Bureau / Type Network
Apres, David Berlow, Font Bureau / Type Network
Astoria, Alan Meeks, Alan Meeks Collection
Bliss, Jeremy Tankard, Jeremy Tankard Typography
Cronos, Robert Slimbach, Adobe Type
Documenta Sans, Frank Blokland, DTL
Dover Sans Text and Display, Robin Mientjes, Tiny Type Co
Edward, Hendrik Weber, form. Ourtype
Granby, Edward Johnston, Elsner + Flake
Halifax, Dieter Hofrichter, Hoftype
Johnston, Edward Johnston, David Farey, ITC
(Johnston) Underground, Edward Johnston, Richard Kegler, P22
London, Henrik Kubel, A2-Type
Mallory, Tobias Frere-Jones, Frere-Jones Type
Metro Office, Akira Kobayashi, Linotype
Mr. Eaves, Zuzana Licko, Emigre
New Atten, Miles Newlyn, Newlyn Type
Relay, Cyrus Highsmith, Occupant Fonts
Rowton Sans, Julien Priez, Hugo Dumont, Jérémie Hornus and Alisa Nowak, form. Font You
Seravek, Eric Olson, Process Type
Today Sans, Volker Küster, Elsner + Flake
Yoga Sans by Xavier Dupret, Monotype
Zeitung, Akiem Helmling, Bas Jacobs, Sami Kortemäki, Underware
I didn’t add links to these to encourage you to look for the foundry site yourself or go to your preferred type website. Licensing from the designers/foundry directly is always best. No middlemen = more reward for the people who did the work. Some of these typefaces are also available for renting, which can be advantageous if you only want to use them for a limited time.