layers

Depending on how you're applying the info, might include avoiding large crowds or weighing risks vs rewards.

Fexofenadine 180mg + famotidine 40mg once daily, or twice daily if you contract COVID or you are exposed to a high-risk situation like being on an airplane. (Famotidine can be substituted with nizatidine 300mg.) Low-dose naltrexone at 0.5mg-4.5mg per day. Amantadine 100mg twice daily especially prior to high-risk exposure and post-exposure or upon contracting COVID. All of these will help prevent long COVID. Amantadine should provide a degree of protection against contracting COVID, although it's likely limited and I wouldn't use it as an alternative to prevention and mitigation efforts like masking up etc.

Hand sanitiser. Use benzalkonium chloride at around 0.1% concentration as an alternative if your skin is sensitive. Can also be used as surface disinfectant at around 0.2% concentration (you can use this concentration for hand sanitising although it's overkill and you're more likely to develop contact dermatitis if you do, although with short-term exposure it's unlikely to cause much trouble.)

You can get benzalkonium chloride as an algaecide. If you do, double check the SDS to ensure that it doesn't contain other active ingredients and make sure you know what you're doing when you calculate the dilution, preferably using distilled or RO water. You should be able to make an staggering amount of surface disinfectant and hand sanitiser this way. Opt for benzalkonium chloride which is designated as cosmetic grade or higher where practical.

I'd probably add a Corsi-Rosenthal box as well, although it only has situational usefulness it's still something worth considering.

Didn't know about neosporin gel (thanks), but Xlear or just saline nasal spray work too.

Air filtration/circulation although you only have limited control of that in some locations. Keeping a window open in a taxi, having a filter in your home, etc. Maybe you can convince your workplace to filter the air too, or bring one yourself if it comes to that. Rosenthal/whoever boxes are cheap to make.

Covixyl is a nasal spray that changes the pH in your nose and blocks the virus. Not as cheap as neosporin or regular petroleum jelly, but it's designed to block covid (with mask also).

There were a couple studies that showed some minor improvement on infection rates from gargling mouthwash containing CPC after possible contact. Certainly couldn't hurt.